The 18-year-old white male developed acute myeloblastic leukemia (AML) 25 months after diagnosis of poorly differentiated lymphocytic lymphoma, diffuse pattern (PDLL-D), involving cervical, supraclavicular, and mediastinal lymph nodes as well as bone marrow. Treatment of the lymphoma consisted of 2,000 rads to the mantel area and 18 months of chemotherapy with intravenous (IV) methotrexate (400 mg/m2), vincristine, and prednisone, alternating every two weeks with IV cyclophosphamide (1,000 mg/m2), vincristine, and prednisone plus monthly intrathecal methotrexate. Thereafter, a complete remission was maintained without therapy until the onset of AML. Several pseudodiploid clones containing multiple structural rearrangements and a hypodiploid clone were identified in the circulating blood at the time of diagnosis of AML. Induction therapy consisting of cytosine arabinoside, 5-azacytidine, vincristine, and prednisone was unsuccessful, and the patient died of sepsis two months after diagnosis. This case calls attention to the increased risk for subsequent acute nonlymphocytic leukemia in patients previously treated for nonhodgkin lymphoma.