The western black crested gibbon (Nomascus concolor), or black gibbon, one of the lesser apes (Hylobatidae), is mainly distributed in Yunnan, China. Of the four recognized subspecies, N. c. jingdongensis is endemic to the Wuliang Mountain, central Yunnan, China. Of all the subspecies, this one has the largest population of any black gibbon. However, the data were all based on brief estimates. We carried out an extensive field survey on population and group distribution of the black gibbon in the Wuliang Mountains by use of loud morning songs and interviews with local people. Ninety-eight groups were confirmed and located in the mid-montane range of Wuliang Mountains. More groups are found on the east slope and the southern region than in the west and the north. Gibbons are more disjunctly distributed on the west slope, especially in the northern part. Deforestation in the late 1950s, 1960s and 1970s was the main reason for rapid loss of habitat and population decline. Hunting was another key reason for population decline and, in many cases, the main reason for local extinction.