The Critically Endangered black crested gibbon Nomascus concolor of China, Laos and Vietnam is threatened by deforestation and habitat destruction but there have been no studies of how it uses its forest habitat, probably because of the typically rugged topography and the species' shyness of humans. We studied the forest use of one habituated group between March 2005 and April 2006 on the border of Wuliangshan Nature Reserve, Wuliang Mountain, Yunnan, southern China. The group spent most of its time in the primary forest but preferred secondary forest in February when Leucosceptrum canum blossomed. They used dwarf forest occasionally but never used Eupatorium adenophorum grassland. Primary forest provided sleeping and singing trees, most food resources, safe cover and suitable locomotion supports. This forest is crucial for their survival but regenerates slowly. Even though secondary forest in the area has been regenerating for >50 years it provides only limited food resources for the gibbons. It may, however, comprise a good corridor for their dispersal. Dwarf forest provides a potential corridor for the group to disperse to a population on the other side of the mountain. Selective logging and agriculture encroachment should be forbidden in the primary forest on Wuliang Mountain. We recommend Alnus nepalensis, Myrica esculenta, L. canum and Betula alnoides as the pioneer species to recover the E. adenophorum grassland and for dispersal corridors.