diff --git a/README.md b/README.md
index c11006b..c954638 100644
--- a/README.md
+++ b/README.md
@@ -328,3 +328,11 @@ Asynchronous readlink(2). Callback gets `(error, linkContents)`, where `linkCont
 #### fs.lstat(path, callback)
 
 Asynchronous lstat(2). Callback gets `(error, stats)`, See `fs.stat`.
+
+#### fs.truncate(path, length, callback)
+
+Asynchronous truncate(2). Callback gets no additional arguments.
+
+#### fs.ftruncate(fd, length, callback)
+
+Asynchronous ftruncate(2). Callback gets no additional arguments.
diff --git a/src/fs.js b/src/fs.js
index 1d03232..a80b5df 100644
--- a/src/fs.js
+++ b/src/fs.js
@@ -943,6 +943,96 @@ define(function(require) {
     }
   }
 
+  function truncate_file(context, path, length, callback) {
+    path = normalize(path);
+
+    var fileNode;
+
+    function read_file_data (error, node) {
+      if (error) {
+        callback(error);
+      } else if(node.mode == MODE_DIRECTORY ) {
+        callback(new EIsDirectory('the named file is a directory'));
+      } else{
+        fileNode = node;
+        context.get(fileNode.data, truncate_file_data);
+      }
+    }
+
+    function truncate_file_data(error, fileData) {
+      if (error) {
+        callback(error);
+      } else {
+        var data = new Uint8Array(length);
+        if(fileData) {
+          data.set(fileData.subarray(0, length));
+        }
+        context.put(fileNode.data, data, update_file_node);
+      }
+    }
+
+    function update_file_node (error) {
+      if(error) {
+        callback(error);
+      } else {
+        fileNode.size = length;
+        fileNode.mtime = Date.now();
+        fileNode.version += 1;
+        context.put(fileNode.id, fileNode, callback);
+      }
+    }
+
+    if(length < 0) {
+      callback(new EInvalid('length cannot be negative'));
+    } else {
+      find_node(context, path, read_file_data);
+    }
+  }
+
+  function ftruncate_file(context, ofd, length, callback) {
+    var fileNode;
+
+    function read_file_data (error, node) {
+      if (error) {
+        callback(error);
+      } else if(node.mode == MODE_DIRECTORY ) {
+        callback(new EIsDirectory('the named file is a directory'));
+      } else{
+        fileNode = node;
+        context.get(fileNode.data, truncate_file_data);
+      }
+    }
+
+    function truncate_file_data(error, fileData) {
+      if (error) {
+        callback(error);
+      } else {
+        var data = new Uint8Array(length);
+        if(fileData) {
+          data.set(fileData.subarray(0, length));
+        }
+        context.put(fileNode.data, data, update_file_node);
+      }
+    }
+
+    function update_file_node (error) {
+      if(error) {
+        callback(error);
+      } else {
+        fileNode.size = length;
+        fileNode.mtime = Date.now();
+        fileNode.version += 1;
+        context.put(fileNode.id, fileNode, callback);
+      }
+    }
+
+    if(length < 0) {
+      callback(new EInvalid('length cannot be negative'));
+    } else {
+      context.get(ofd.id, read_file_data);
+    }
+  }
+
   function validate_flags(flags) {
     if(!_(O_FLAGS).has(flags)) {
       return null;
@@ -1505,14 +1595,38 @@ define(function(require) {
     lstat_file(context, path, check_result);
   }
 
-  function _truncate(path, length, callback) {
-    // TODO
-    //     if(!nullCheck(path, callback)) return;
+  function _truncate(context, path, length, callback) {
+    if(!nullCheck(path, callback)) return;
+
+    function check_result(error) {
+      if(error) {
+        callback(error);
+      } else {
+        callback(null);
+      }
+    }
+
+    truncate_file(context, path, length, check_result);
   }
 
-  function _ftruncate(fd, length, callback) {
-    // TODO
-    //     if(!nullCheck(path, callback)) return;
+  function _ftruncate(fs, context, fd, length, callback) {
+    function check_result(error) {
+      if(error) {
+        callback(error);
+      } else {
+        callback(null);
+      }
+    }
+
+    var ofd = fs.openFiles[fd];
+
+    if(!ofd) {
+      callback(new EBadFileDescriptor('invalid file descriptor'));
+    } else if(!_(ofd.flags).contains(O_WRITE)) {
+      callback(new EBadFileDescriptor('descriptor does not permit writing'));
+    } else {
+      ftruncate_file(context, ofd, length, check_result);
+    }
   }
 
 
@@ -1723,6 +1837,28 @@ define(function(require) {
     );
     if(error) callback(error);
   };
+  FileSystem.prototype.truncate = function(path, length, callback) {
+    callback = maybeCallback(callback);
+    var fs = this;
+    var error = fs.queueOrRun(
+      function() {
+        var context = fs.provider.getReadWriteContext();
+        _truncate(context, path, length, callback);
+      }
+    );
+    if(error) callback(error);
+  };
+  FileSystem.prototype.ftruncate = function(fd, length, callback) {
+    callback = maybeCallback(callback);
+    var fs = this;
+    var error = fs.queueOrRun(
+      function() {
+        var context = fs.provider.getReadWriteContext();
+        _ftruncate(fs, context, fd, length, callback);
+      }
+    );
+    if(error) callback(error);
+  };
 
   return {
     FileSystem: FileSystem,
diff --git a/tests/spec/fs.truncate.spec.js b/tests/spec/fs.truncate.spec.js
new file mode 100644
index 0000000..a9fe563
--- /dev/null
+++ b/tests/spec/fs.truncate.spec.js
@@ -0,0 +1,278 @@
+define(["IDBFS"], function(IDBFS) {
+
+  describe('fs.truncate', function() {
+    beforeEach(function() {
+      this.db_name = mk_db_name();
+      this.fs = new IDBFS.FileSystem({
+        name: this.db_name,
+        flags: 'FORMAT'
+      });
+    });
+
+    afterEach(function() {
+      indexedDB.deleteDatabase(this.db_name);
+      delete this.fs;
+    });
+
+    it('should be a function', function() {
+      expect(typeof this.fs.truncate).toEqual('function');
+    });
+
+    it('should error when length is negative', function() {
+      var complete = false;
+      var _error, _result;
+      var that = this;
+
+      var contents = "This is a file.";
+
+      that.fs.writeFile('/myfile', contents, function(error) {
+        if(error) throw error;
+
+        that.fs.truncate('/myfile', -1, function(error) {
+          _error = error;
+          complete = true;
+        });
+      });
+
+      waitsFor(function() {
+        return complete;
+      }, 'test to complete', DEFAULT_TIMEOUT);
+
+      runs(function() {
+        expect(_error).toBeDefined();
+      });
+    });
+
+    it('should error when path is not a file', function() {
+      var complete = false;
+      var _error, _result;
+      var that = this;
+
+      that.fs.truncate('/', 0, function(error) {
+        _error = error;
+        complete = true;
+      });
+
+      waitsFor(function() {
+        return complete;
+      }, 'test to complete', DEFAULT_TIMEOUT);
+
+      runs(function() {
+        expect(_error).toBeDefined();
+      });
+    });
+
+    it('should truncate a file', function() {
+      var complete = false;
+      var _error, _result;
+      var that = this;
+
+      var buffer = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);
+      var truncated = new Uint8Array([1]);
+
+      that.fs.open('/myfile', 'w', function(error, result) {
+        if(error) throw error;
+
+        var fd = result;
+        that.fs.write(fd, buffer, 0, buffer.length, 0, function(error, result) {
+          if(error) throw error;
+
+          that.fs.close(fd, function(error) {
+            if(error) throw error;
+
+            that.fs.truncate('/myfile', 1, function(error) {
+              _error = error;
+
+              that.fs.readFile('/myfile', function(error, result) {
+                if(error) throw error;
+
+                _result = result;
+                complete = true;
+              });
+            });
+          });
+        });
+      });
+
+      waitsFor(function() {
+        return complete;
+      }, 'test to complete', DEFAULT_TIMEOUT);
+
+      runs(function() {
+        expect(_error).toEqual(null);
+        expect(_result).toEqual(truncated);
+      });
+    });
+
+    it('should pad a file with zeros when the length is greater than the file size', function() {
+      var complete = false;
+      var _error, _result;
+      var that = this;
+
+      var buffer = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);
+      var truncated = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8, 0]);
+
+      that.fs.open('/myfile', 'w', function(error, result) {
+        if(error) throw error;
+
+        var fd = result;
+        that.fs.write(fd, buffer, 0, buffer.length, 0, function(error, result) {
+          if(error) throw error;
+
+          that.fs.close(fd, function(error) {
+            if(error) throw error;
+
+            that.fs.truncate('/myfile', 9, function(error) {
+              _error = error;
+
+              that.fs.readFile('/myfile', function(error, result) {
+                if(error) throw error;
+
+                _result = result;
+                complete = true;
+              });
+            });
+          });
+        });
+      });
+
+      waitsFor(function() {
+        return complete;
+      }, 'test to complete', DEFAULT_TIMEOUT);
+
+      runs(function() {
+        expect(_error).toEqual(null);
+        expect(_result).toEqual(truncated);
+      });
+    });
+
+    it('should update the file size', function() {
+      var complete = false;
+      var _error, _result;
+      var that = this;
+
+      var buffer = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);
+
+      that.fs.open('/myfile', 'w', function(error, result) {
+        if(error) throw error;
+
+        var fd = result;
+        that.fs.write(fd, buffer, 0, buffer.length, 0, function(error, result) {
+          if(error) throw error;
+
+          that.fs.close(fd, function(error) {
+            if(error) throw error;
+
+            that.fs.truncate('/myfile', 0, function(error) {
+              _error = error;
+
+              that.fs.stat('/myfile', function(error, result) {
+                if(error) throw error;
+
+                _result = result;
+                complete = true;
+              });
+            });
+          });
+        });
+      });
+
+      waitsFor(function() {
+        return complete;
+      }, 'test to complete', DEFAULT_TIMEOUT);
+
+      runs(function() {
+        expect(_error).toEqual(null);
+        expect(_result.size).toEqual(0);
+      });
+    });
+
+    it('should truncate a valid descriptor', function() {
+      var complete = false;
+      var _error, _result;
+      var that = this;
+
+      var buffer = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);
+
+      that.fs.open('/myfile', 'w', function(error, result) {
+        if(error) throw error;
+
+        var fd = result;
+        that.fs.write(fd, buffer, 0, buffer.length, 0, function(error, result) {
+          if(error) throw error;
+
+          that.fs.ftruncate(fd, 0, function(error) {
+            _error = error;
+
+            that.fs.fstat(fd, function(error, result) {
+              if(error) throw error;
+
+              _result = result;
+              complete=true;
+            });
+          });
+        });
+      });
+
+      waitsFor(function() {
+        return complete;
+      }, 'test to complete', DEFAULT_TIMEOUT);
+
+      runs(function() {
+        expect(_error).toEqual(null);
+        expect(_result.size).toEqual(0);
+      });
+    });
+
+    it('should follow symbolic links', function() {
+      var complete = false;
+      var _error, _result, _result2;
+      var that = this;
+
+      var buffer = new Uint8Array([1, 2, 3, 4, 5, 6, 7, 8]);
+
+      that.fs.open('/myfile', 'w', function(error, result) {
+        if(error) throw error;
+
+        var fd = result;
+        that.fs.write(fd, buffer, 0, buffer.length, 0, function(error, result) {
+          if(error) throw error;
+
+          that.fs.close(fd, function(error) {
+            if(error) throw error;
+
+            that.fs.symlink('/myfile', '/mylink', function(error) {
+              if(error) throw error;
+
+              that.fs.truncate('/mylink', 0, function(error) {
+                _error = error;
+
+                that.fs.stat('/myfile', function(error, result) {
+                  if(error) throw error;
+
+                  _result = result;
+                  that.fs.lstat('/mylink', function(error, result) {
+                    if(error) throw error;
+
+                    _result2 = result;
+                    complete=true;
+                  });
+                });
+              });
+            });
+          });
+        });
+      });
+
+      waitsFor(function() {
+        return complete;
+      }, 'test to complete', DEFAULT_TIMEOUT);
+
+      runs(function() {
+        expect(_error).toEqual(null);
+        expect(_result.size).toEqual(0);
+        expect(_result2.size).not.toEqual(0);
+      });
+    });
+  });
+});
\ No newline at end of file
diff --git a/tests/test-manifest.js b/tests/test-manifest.js
index 0f30a63..72c44a9 100644
--- a/tests/test-manifest.js
+++ b/tests/test-manifest.js
@@ -26,6 +26,7 @@ define([
   "spec/fs.lseek.spec",
   "spec/fs.symlink.spec",
   "spec/fs.readlink.spec",
+  "spec/fs.truncate.spec",
   "spec/path-resolution.spec",
 
   // IDBFS.FileSystem.providers.*