Adult male and female Callidiellum rufipenne (Motschulsky) (Coleoptera: Cerambycidae) aggregate on severely stressed or fallen trees and cut logs of cypress species (Cupressaceae) that are the hosts of their larvae. Our studies showed that male C. rufipenne actively search for females on these trees and only respond to females after contacting them with their antennae. Removing cuticular hydrocarbons from fresh carcasses of females with solvent rendered the carcasses unattractive to males, but activity was restored when the solvent extract was reapplied. These findings suggest that contact pheromones mediate mate recognition in this species. Bioassays of fractions of the extracts determined that the branched chain hydrocarbon fraction was primarily responsible for activity. 5,17-Dimethylnonacosane was a key sex-specific component in extracts of females, and synthetic 5,17-dimethylnonacosane elicited a strong mating response from males. We conclude that this compound is an important component of the contact sex pheromone of C. rufipenne if not the sole component. Solvent extracts of both sexes also contained 9-pentacosyne and 9-heptacosyne. To our knowledge, this is only the second report of alkynes in the cuticular lipids of insects.