Many species of pest aphids reproduce sexually on the winter host. The sex pheromone of the vetch aphid, Megoura viciae, has recently been identified as comprising the,(4aS,7S,7aR)- isomers of nepetalactone and nepetalactol. The stereochemistry at carbon-1 of the lactol was not defined, but is now shown, by X-ray crystallography on the 3,5- dinitrobenzoate ester, to have the R configuration, This lactol is the major product from reduction of the lactone with diisobutylaluminium hydride. Results from the similar reduction of other nepetalactone isomers are presented.