We tested the hypothesis that contact pheromones mediate mate recognition in Prionus californicus Motschulsky, a species of longhorned beetle (Coleoptera: Cerambycidae) in the primitive subfamily Prioninae. Males attempted to mate with live females only after contacting them with their antennae, and 80% of males showed an identical response to freshly killed females. Males did not attempt to mate with dead females that had been extracted with solvent, suggesting that mate recognition cues had been eliminated. When the solvent extract was applied to carcasses of the same dead females, however, 56% of the males again attempted to mate with them. A preliminary analysis of crude solvent extracts of adult beetles revealed that adults have at least 24 different cuticular hydrocarbons and that the sexes differ in relative proportions of some compounds that may serve as the contact pheromone. This report provides the first evidence that contact pheromones play an important role in mate recognition in the more primitive longhorned beetles.