Abstract: Sun bear is found in Burma,Thailand,Vietnam,Sumatra,Borneo,North-east of India,Malaysia,and Yunnan and Sichuan of China and has been listed in 1990 IUCN Red List of Threatened Animals as a vulnerable species.In this paper,a total of 1174 bases of mitochondrial DNA sequence (397 bases of cytochrome b gene,346 bases of 12S Rrna gene,98 bases of Trna genes,and 333 bases of D-loop region) from each of four sun bears from different collections have been sequenced.Comparing with the black rhino Trna genes,our results suggest that the loop regions of Trna genes evolve much fast than the stem regions.In the cytochrome b gene,12S Rrna gene and Trna gene regions,no sequence variation among the individuals was observed,which indicates that genetic variability in the sun bear is relatively low.In the D-loop region,there are 13 and 1 sites,respectively,characterized by transition and transversion among the 4 sun bears sequenced.The relationships among all the individuals were fully resolved based on mitochondrial D-loop sequences by using parsimony analysis.Our results suggest that the mitochondrial D-loop region is very useful for population genetic study of the sun bear.