Karyotypes of six species (one of the six species is represented by three subspecies) of the treefrogs (Rhacophoridae) were described and compared. All species have 2n=26 chromosomes consisting of five large and eight small chromosome pairs, indicating a close relationship between Rhacophoridae and Ranidae. Karyological as well as ecological comparisons suggest the three groups; (1)Rhacophorus schlegelii, R. viridis amamiensis, R. v. viridis, andR. v. owstoni, (2)R. buergeri, R. robustus, andR. japonicus, and (3)R. eiffingeri.These groupings are consistent with those on the morphological bases.