White-cheeked gibbon(H. leucogenys) is distributed in the south of Yunnan, China.The chromosomes of a female and a male were studied by several banding techniques(G-,C -and Ag-staining), and a techniqe for simultaneous exhibiting chromosome replication patterns and late replicating Y chromosome. The diploid chromosome number is 52. There are 22 pairs of metacentrlcs or submetacentrics (No. 1-22); 3 pairs of acrocentrics(Nos. 23-25), and chromosomes Nos. 23-24 with a secondary constriction near the centromere on the short arm.The X chromosome is a large metacentric, and the Y, the smallest acrocentric. Its karyotype for mula is 44(M or SM)+ 6(A), XY(M, A). The centrimeric distribution of heterochromatin has been demonstrated in some chromosomes. In addion, there are 3 kinds of heterochromatin on the chromosomes:(1) ab sent of centromeric heterochromatin,(2) interstitial heterochromatin,(3) terminal heterochromatin.Interstitial heterochromatin has been observed on the blarm of X chromosome. Y chromosome is completely C-band positive. Silver staining revealed 5 chromosomes with NORs in the male specimen.4 Ag-NORs of theth are heated on the secondary constriction of chromosomes 23 and 24 respectivly,and one of them is located on the Y chromosome which has been confirmed by Fluorescence in situ hybridization(FISH) in the same cell. There are 4 chromosomes with Ag-NORs in the female specimen,and they are also located on the secondary constriction of chromosomes 23 and 24. Moreover,the association of Ag-NORs have been observed. Base on the above results,the relationship in gibbons and the way of chromosome evo lution in the genus Hylobates have been discussed.