Genetic variants of plasma alpha-amylase and erythrocyte carbonic anhydrase in the musk shrew (Suncus murinus) were found by electrophoreses using cellulose acetate plates. It was demonstrated that phenotypic differences of alpha-amylase are controlled by two codominant alleles (Amy-1a and Amy-1b) at a single autosomal locus (Amy-1). The segregation data of the carbonic anhydrase phenotypes in the progeny supported the genetic theory of two codominant alleles (Car-1a and Car-1b) at a single autosomal locus (Car-1). The data suggested that there was no close linkage between the two loci, Amy-1 and Car-1. The Car-1 locus was fixed with one of the two alleles in each of the four lines, i.e. Nag, Oki , Tar and Jak originating from wild animals captured in Nagasaki and Naha and Tarama Island, Okinawa, Japan, and in Jakarta, Indonesia, respectively. Oki and Tar lines still showed segregation of the two alleles at the Amy-1 locus.