Four members of the Chemosensory protein (CSP) gene family have been cloned from the spruce budworm, Choristoneura fumiferana. CSPs, also known as OS-D-like proteins, are a family of small soluble proteins associated with insect sensory organs, including the sensillum lymph in some cases. A role in odorant transport, similar to insect odorant binding proteins (OBPs), has been proposed. An analysis of all known insect CSP sequences revealed several homologous subgroups, characterized either by the retention of, or diversion from, several highly conserved amino acid motifs. The developmental, sex and tissue specific expression of four CSP genes from the spruce budworm was determined, and each yielded unique patterns. One CSP gene (retains the highly conserved amino acid motifs) was detected only in the adult stage, and not in larval or pupal stages; two CSP genes (characterized by diversion from the conserved amino acid motifs) were detected only in the larval and pupal stages (not in the adult stage); and, one gene was detected in all stages. Two of the three genes expressed in larvae were detected specifically in stages undergoing ecdysis, such as the 5^th to 6^th instar molt, while expression of the third peaked immediately prior to the prepupal stage. Based on expression patterns, CSPs from the spruce budworm may function in insect development. Next, CSPs from the spruce budworm will be expressed in bacteria, and purified for antibody production and ligand binding studies.