Three adult patients with acute myelocytic leukemia have been observed with complete remissions lasting from 2 1/2 to 9 1/2 years. Maintenance chemotherapy was not required during the period of remission. During the time in which these patients were treated initially, there were 177 other adults with acute myelocytic leukemia. Eight of these had complete remissions of six months' duration or less. No clinical, laboratory, or therapeutic differences distinguished those patients who experienced remission from those who did not. The infrequency of remission in patients above the age of 45 was confirmed. Five patients were observed to have relatively prolonged survival despite the failure of therapy to induce remission of clinically indolent, "smoldering" leukemia which was acute on morphologic grounds. Mechanisms as yet unrecognized, and possibly inherent in the host, may have been predominant in determining the course and prognosis.