A 46-year-old man treated with azathioprine (100-150 mg/day) and prednisolone (10mg/day) for 14 years after allogeneic renal transplantation, was admitted to our hospital in December, 1988 for the evaluation of leukocytosis. His leukocyte count was 32,700/microliters with 38% monocytes and 2% blasts. Chromosomal analysis of the bone marrow revealed 45, XY, -7. He was diagnosed as chronic myelomonocytic leukemia (CMML), and treated with low-dose Ara-C. Two months later, he progressed to overt acute leukemia, and he complained of difficulty in swallowing. Endoscopic examination revealed esophageal cancer. The patient died of respiratory failure on April 18, 1989. This case suggests that immunosuppressive agents might play an important role on the pathogenesis of CMML and esophageal cancer.