1. The distribution of the bivalves of fresh-water in Korea and the morphological variation of shells in different localities were undertaken over a period of 17 months from April, 1975 to September, 1976 at 103 stations as a shown in Fig. 1. 2. Ten species of the bivalves were identified: Corbicula fluminea, C. felnouilliana, Anodonta woodiana, Cristaria plicata, Solenaia triangulars, Unio douglasiae, Lanceolaria acrorhyncha, Lamprotula gottschei, L. coreana, Limnoperma lucustris (Table 1) 3. The dominant species of the bivalves were Corbicula fluminea at 11 areas, Cristaria plicata at 10 areas, Unio douglasiae at 9 areas in south Korea, respectively(Table 1.) 4. The bivalves were collated as follow: C. felnouilliana was found in the Han, the Geum, the Negdong, the Yeongsan and the Dongjin river. S. triangularis was found in the Han and the Boseong river. L. acrorhyncha was found in the Han, the Nagdong, the Geum, the Seom jin, the Mangyeong, the Boseong and the Tam jin river. L. gottschei was found in the Han, the Geum, the Seomjin, the Yeongsan, the Boseong and the Tam jin river. L. coreana was found in the Han, the Nagdong, the Geum, the Yeongsan and the Boseong river. L. lucustris was found in the Han, the Nagdong, the Geum, the Seom jin river respectively. 5. H/L, H/B values of C, fluminiea of shell in the branch-stream were less than that of the downstream, and H/L, H/B values of it in the uppor-stream were the least. B/L values of it in the upper stream were less than that of the downstream, and B/L values of it in the branch stream were the least. H/L, B/L values of it had a tendency to be increased from the branch stream to the mainstream. H/L values of the shell in the Nagdong, the Han and the Seomjin rivers which its length is longer and its flux is more abundand than other rivers were bigger and H/B values of the shell in the northern parts of the Mangyeong river were less than that of southern parts of the Mangyeong river. Also, B/L values of the shell in the northern parts of Korea as the Han river etc had a tendency to be increased than in the other rivers. 6. Morphological variation of shell of U. douglasiae which lives in the longer rivers as the Nagdong, the Han, the Geam river was longer and flatter in its shell-length than that of other rivers.