The trans-1; trans-5-, trans-1, cis-5-, and cis-1, trans-5 stereoisomers of N-isobutylnona-l:5-diene-l-carboxy-amide were synthesized. The trans-1, trans-5 compound is identical with a previously described isomer of unproven configuration. Since the cis-1, cis-5 compound is already known, the 4 possible geometric isomers are now available. The configurations, assigned on a basis of reaction stereo-specificity, are supported by spectroscopic investigation. All of the compounds are poor sialogogues and have low insecticidal potencies. None is identical with natural pellitorine and the currently accepted structure is incorrect. Nevertheless, it has been possible to re-isolate pellitorine and establish its identity with the material described by Jacobson.