A two-choice type bioassay has been used to screen extracts from a number of plants of the sagebrush community for their antifeeding properties against the Colorado potato beetle, Leptinotarsa decemlineata Say. The extracts of Artemisia tridentata, Purshia tridentata and Chrysothamnus nauseosus have been fractionated for their antifeeding constituents. Known constituents of these plants (deacetalmatricarin, coumarins, cucurbitacins, polyphenols, polyacetylenes, and essential oils) were also screened. The results indicate that several chemical classes of compounds are responsible for antifeeding activity in each plant. Water soluble substances present in the waste marc after steam distillation of peppermint oil were highly active, too.