Abstract: A traditional classification of the gibbons recognised a single genus,Hylobates,with four subgenus (Groves,1972;Prouty et al.,1983).The Concolor or Crested Gibbons were placed in the subgenus Nomascus,and assigned to one species,H.(N.) concolor.To this species was assigned six subspecies,as follows:H.c.concolor (North vietnam and Laos,between the Red and Black Rivers),hainanus (Hainan Island,China),lu (a small area in far western Laos),leucogenys (Other parts of northern Vietnam and Laos),siki (Central Vietnam,southern Laos),gabriellae (South Vietnam).The adult males (and juveniles of both sexes) are completely black in the first three,but have light (white to pale reddish) cheek patches in the other three;the adult female are buffy coloured (with a blackish streak from crown to nape) in all,but in concolor and lu the ventral region is blackish.