Different odorant-binding proteins (OBPs) were isolated from total antennal homogenates of male and female Bombyx mori. Proteins were separated according to their isoelectric point by using preparative fast-flow isoelectrofocusing. Odorant-binding proteins were identified in immunoblots by antisera raised against the pheromone-binding protein (anti-PBP) and the general odorant-binding protein (anti-GOBP2) of Antheraea polyphemus. Four proteins cross-reacting with anti-PBP were detected in males and two in females, while three proteins cross-reacting with anti-GOBP2 were found in males and five in females. Both anti-PBP and anti-GOBP2 cross-reacting proteins had an apparent molecular weight of 15–16 kDa. In parallel, the same two antisera were used in immunocytochemical studies in order to determine the distribution of these proteins within the various subtypes of olfactory sensilla. The presence of multiple odorant-binding proteins within one moth species as well as their complex distribution pattern support the suggestion that soluble OBPs might have a function in odorant discrimination. Chem. Senses 22: 503–515, 1997.