Rearrangements in the DNA of chronic myelogenous leukemia patients of Chinese, Malay and Indian origin were detected in the breakpoint cluster region of chromosome 22 using molecular techniques. The DNA of fifty patients was examined using a 1.2 kb DNA probe. Rearrangements were detected in 46/50 patients. Karyotypic data were available in nine patients, all of whom were Philadelphia chromosome positive and exhibited DNA rearrangement. Detection of the Philadelphia translocation by molecular methods, at this institution, where cytogenetics is not routinely performed, confirms its diagnostic value. The rearrangement data obtained in this study is consistent with molecular features of chronic myelogenous leukemia patients of Western countries.