In the mussel, Mytilus galloprovincialis, there were three kinds of tropomyosin isoforms, which were designated as TM1, TM2 and TM3, respectively. It had been reported that TM1 was contained as only tropomyosin isoform and major component in the muscle tissues such as adductor and cardiac muscles, it was confirmed as the major isoform in adductor, cardiac and anterior pedal retractor muscles, and in the mantle and gills. In this present study, meanwhile, TM2 and TM3 were detected as two new isoforms in the mantle and gills. TM2 and TM3 existed only in the mantle and in both the mantle and gills, respectively. Both TM2 and TM3 were minor isoforms compared to TM1. TM2 had almost the same molecular weight as TM1 whereas TM3 had lower molecular weight than TM1. Moreover, TM3 had more basic isoelectric point than TM1 and TM2.