A spontaneous complete remission of 34 months' duration was observed in an adult patient with acute myeloblastic leukemia. The remission occurred after a severe febrile pneumonia, which was treated with leukocyte transfusions. At relapse, chromosomal abnormalities reappeared slowly. Such spontaneous complete remissions, almost always associated with bacterial infections and blood transfusions, are extremely rare, and are usually of short duration. Previous cases are summarized, and the role of etiologic factors, including those related to the leukemic proliferation, are discussed.