Abstract: Mitochondrial DNAs purified from the livers of P.phayrei and P.francoisi were analyzed with 15 restriction endonucleases.From the 156 bp recognition enzymes used,41-50 sites were observed in the samples.By combining the cleavage patterns for each enzyme,the four samples were classified into four restriction types.The estimated number of nucleotide substitutions per site in P.phayrei,P.francoisi and between the two species was 0.007,0.006 and 0.038,respectively.In combination with our previous data on Macaca mulatta and M.arctoides,the molecular phylogenetic trees of these four species were constructed by the unweighted-pair-group method and the neighbor-joining method.These results provide evidence that intraspecific divergence of P.phayrei and P.francoisi began aout 0.3 Mybp,and that interspecific divergence between these two species and between Colobinae and Cercopithecinae began about 1.9 Mybp and before 11 Mybp,respectively.