Genomic DNA from the muscle of marsh clam (Corbicula leana) from Gochang, Muan and a Chinese site was extracted to identify genetic differences and similarity by randomly amplified polymorphic DNAs-polymerase chain reaction (RAPD- PCR). Out of 20 primers, seven primers produced amplified fragments which were consistently polymorphic. A total of 1,246 amplified products were produced of which 530 were polymorphic $(42.5\%)$. The number of polymorphic bands produced per primer varied from 40 to 122 with an average of 75.7 in marsh clam from Gochang. 3.28 of the 23.0 polymorphic bands per lane were found to be polymorphic. Also, about $4.34\%$ of total polymorphic bands were specific to marsh clam from Gochang. The major common bands of 0.28 kb generated by primer OPB-15 (GGAGGGTGTT) were present in every individuals, which were polymorphic. This common bands in every individuals should be diagnostic of specific strains, species and/or their relatedness. Primer OPB-19 (ACCCCCGAAG) produced the highest number of 12 specific bands. The intra-population variation was revealed in the band patterns identified by this primer. The random primer OPB-12 (CCTTGACGCA) yielded the amplified fragments which were consistently polymorphic between the marsh clams from Gochang and from Muan. This primer produced a total of 77 polymorphic bands: 31 bands from Gochang, 14 from Muan and 32 from the Chinese populations. An average of polymorphic bands were 1.8 from Gochang and 2.5 from the Chinese populations. This value obtained from the Chinese population was higher than those from the two domestic populations. Generally, the RAPD polymorphism generated by these primers may be useful as a genetic marker for strain or population identification of marsh clam.