The present taxonomical review was conducted to investigate differeces among seven populations of Korean crucian carp (C. a. langsdorfi), and difference Korean crucian carp and one species of Japanese crucian carp (C. a. subsp.), by the electrophoretic patterns of muscle proteins. Their electropherograms were exmined and the percentage similarities were caculated according to the fomular of Whitney et al. (1968). The average similarity of Korean seven poprlations was 92%. This data suggest that Korean curcian carp is all conspecific since there was no significant difference among protein patterns of populations. Meanwhile, in the protein patterns of C. a. langsdoyfi and C. a. subsp., a few specific fractions were detected, thus their similarity was 66%. The present similarity was very similar to the average intraspecific similaries forund in other vertebrates, and was low enough to treat these fishes as two good species. Therefore, it is assumed that these fishes must be classified as two independent species rather than subspecies. In order to a firm conviction on the present results, further intensive review by verious analytic methods should be carried out in the future.