Restriction fragment analysis was used to measure mitochondrial DNA (mtDNA) variation within and between the genera Enhydris and Elaphe(snakes), inhabiting in Thailand, Japan and South Korea. Purified mtDNAs were digested with 10 restriction endonucleases. In this analysis, three different mtDNA sizes, 17.5 18.0 and 19.5kb, were observed. The mtDNA of Elaphe dione has two different sizes, one is 18kb and the other is 19.5kb. This intraspecific variation in genome size could be attributed to an addition or deletion of about 1.5kb fragment. In Elaphe quadrivirgata, heteroplasmy showing mtDNA restriction site differences was identified. The comparisons of restriction fragments. enabled the estimation of the levels of fragment homology (F value) and nucleotide sequence divergence(p value). Mean p values of within and between 6species of the genera Enhydris and Elaphe were 0.023 (0.003-0.101) and 0.119(0.086-0.189), respectively. Between two genera, the mean p value was 0.133, ranging from 0.094 to 0.196. Presumed range of divergent times, based on the p value, within and between two genera was about 4.3-7.2 million years ago.