 The structure of acetyl cyanide was determined through the joint use of electron diffraction intensities and rotational constants.These values helped to determine that the average thermal bond distances are 1.116±0.011 Å, 1.167±0.010 Å, 1.208±0.009 Å, 1.477±0.008 Å and 1.518±0.009 Å. Additionally, the bond angles in the structure 124.6±0.7°, 114.2±0.9°, 179.2±2.2° and 109.2±0.7°.This places the single C-C bond at a larger bond distance than the bonds within the vinylacetylene, acrylonitrile and propynal molecules.