The authors analyzed the PvuⅡ, HindⅢ and BgⅢ restriction enzyme mappings of seven cases of chronic myeloid leukemia, using a v-abl probe labeled by α-³²P-dCTP. The results showed that the PvuⅡ and HindⅢ mappings of three cases among the seven had been remarkably altered and the multiple changes of PvuⅡ sites had been observed, as compared with the normal subjuct. Therefore, the authors predicted that Ph chromasomal rearrangement in this kind of chronic myeloid leukemia could involve the inside of c-abl oncogene and might be a multiple rearrangement as well.