Carbon-13 NMR chemical shifts are reported for a series of seventeen olefins with tetra-, tri-, di-and mono-snbstitution by nitrile and methoxycarbonyl groups. Analyses of the data for the nitrile, methoxy and carbonyl chemical shifts by mnltiple linear regression provide a good correlation with the pattern of geminal, c h i d and transoid substitution. The olehic shielding data are more complicated, and the analysis requires the introduction of pairwise additivity parameters. It seems likely that the greater complexity arises from steric effects associated with ckoid and geminal methoxycarbonyl substituents, which produce deviations from planarity. The empirical relationships, which are reported here, are useful in removing several ambiguities in the spectral assignments. In this series of compounds it is also observed that substituents which are cis to the nitrile, shift the nitrile resonance 1-2ppm to high field of those for the trans snbstituents.