This is a description of the exoskeleton and musculature of the abdomen of the adult tobacco hornworm, Manduca sexta (Lepidoptera: Sphingidae). In both sexes segments 1 and 2 are specialized for movement of the abdomen. Segments 3 through 6 are similar and have a generalized structure. Segments 7 through 10 are specialized for mating and oviposition. In males, segment 2 has developed additional muscles for everting the scent brush. Where possible, the abdominal muscles of Manduca have been homologized with those of other Lepidoptera.