Previously, we purified a protein with a molecular mass of 10 kDa (p10) that increases transiently during the regeneration of legs in the nymphal American cockroach Periplaneta americana, and showed that it is localized exclusively in the cytosol and on the external side of the newly formed epidermis of the regenerating legs [Nomura, A. et al. (1992) Int. J. Dev. Biol. 36, 391-389]. We isolated p10 cDNA and analyzed the expression of the p10 gene. The results indicated that p10 is synthesized as a precursor protein with a putative prosegment including a signal sequence at its N-terminal. The deduced amino acid sequence of p10 showed 53% and 47% identities with those of A10 (a Drosophila antennal protein) and CLP-1 (a moth, Cactoblastis cactorum labial palp protein), respectively. Expression of the p10 gene was shown to be significantly enhanced in regenerating Periplaneta legs. Immunoblotting analysis revealed that p10 was expressed not only in the regenerating legs, but also in the antennae and heads of nymphal and adult cockroaches.