The classification and phylogenetic relationships of the snub-nosed langurs (Rhinopithecus) are still open questions. We have sequenced a mitochondrial cytochrome b gene fragment from R. roxellana, R. bieti, R. avunculus and Presbytis phayrei. There are 47 sites (19%) characterized by variation. A series of evolutionary trees with concordant topology has been derived by using parsimony, maximum likelihood and distance methods, which may have resolved the evolutionary relationships of the three golden monkey species. R. bieti is more closely related to R. avunculus than to R. roxellana. The divergence among those three species occurred about 2-6 million years ago. Our results suggest that Rhinopithecus is a valid genus, and avunculus should be placed into this genus. Our non-invasive genetic analysis provided useful information for the genetic management of the captive population at the Kunming Institute of Zoology.