The genetic relationships of four species of frogs, genus Rana, from Yunnan, China, were investigated using starch gel electrophoresis of isozymes. Rana chaochiaoensis, R. pleuraden, R. phrynoides and R. limnocharis, representing four different species groups, were compared to each other and to representative species from other parts of Asia: R. amurensis from eastern Siberia, R. japonica from Japan, and R. nigromaculata from Korea. Twenty-four isozyme loci were reliably detected and scored, of which all but one were variable. R. chaochiaoensis, R. japonica and R. amurensis, all members of the Eurasian "brown frog" group, clustered together as a group although genetic distances were comparatively high. The "pond frogs", R. nigromaculata and R. pleuraden, similarly clustered together. Both R. phrynoides and R. limnocharis were highly divergent from the other species, but R. phrynoides seemed to be more closely affiliated with the "pond frogs" than with the "brown frogs". The data indicate that the highly enigmatic 64-chromosome karyotype of R. phrynoides arose from among 26-chromosome ancestors. The relationships of R. limnocharis cannot be precisely defined. Genetic divergence among Asiatic Rana appears to be very high.