The terpene components of extracts prepared from male Lutzomyia longipalpis (Diptera: Psychodidae) collected from four sites in Honduras and one in Costa Rica mere analysed by high-performance liquid chromatography, gas chromatography and coupled gas chromatography -mass spectrometry. The terpene components of Lu. longipalpis from other regions of South America have previously been shown to be sex pheromones. The flies from the four areas of Honduras, where Leishmania chagasi infection may lead to visceral or atypical cutaneous leishmaniasis, mere found to be homogenous, all producing 9-methylgermacrene-B. Three types of terpene (9-methylgermacrene-B, a novel homosesquiterpene and a small amount of diterpene) were detected in pools of flies from Liberia, Costa Rica, where only atypical cutaneous leishmaniasis has been found. These results indicate that there are probably at least two and possibly three distinct populations of Lu. longipalpis in this region. The clinical manifestation of Leishmania chagasi infection does not appear to be dependent on which population of Lu. longipalpis transmitted the parasite.