Molecular weights of the skeletal muscle myosin, actin, troponin C and tropomyosin were compared in two frog species, Hyla japonica and Xenopus tropicalis, by SDS-PAGE and Western blot. Polyclonal antibody was produced using H. japonica skeletal muscle as the antigen. Polyclonal antibodies to nematode (Caenorhabditis elegans), mold slime (Physarum polycephalum), crab (Pagurus japonicus) and chicken skeletal muscle were also used. In H. japonica, the molecular weights of skeletal myosin, actin, troponin C and tropomyosin were 230, 42, 19 and 38 kDa, respectively, by using anti-C. elegans paramyosin, anti-P. polycephalum actin, anti-crab troponin C and anti-chicken gizzard tropomyosin antibodies. Molecular weights of the same proteins in X. tropicalis detected by the same antibodies were 230, 43, 20 and 40 kDa, respectively. In total, 29 protein bands were detected in H. japonica skeletal muscle and 24 bands in X. tropicalis by SDS-PAGE. The results revealed interspecific differences in molecular weights of selected skeletal muscle proteins and in the total skeletal muscle protein profiles between the two frog species.