A patient who developed Philadelphia (Ph) chromosome-positive chronic myelogenous leukemia (CML) 8 years after successful treatment for Hodgkin's disease (HD) is reported. The Ph chromosome with a typical 9(22) translocation was identified by banding techniques in 80% of bone marrow (BM) cells. Southern blot analysis showed breakpoint cluster region (BCR) rearrangement as observed in classical CML. Until now, only three cases of Ph + CML have been reported after treatment for HD. At present, it is not clear whether development of CML after HD represents a therapy-induced complication, an increased susceptibility to secondary malignancies owing to the malignant process itself, a consequence of the immunological deficiencies in HD, or possibly a genetic susceptibility to malignancy.