Thirteen male patients with acute myelogenous leukemia who, on bone marrow chromosome analysis, were missing all or part of the Y chromosome were treated at this institution between 1975 and 1983. Giemsa-banding techniques were performed in 12 cases. Twelve showed -Y in at least 80% of bone marrow metaphases, and one patient had 25% 46,XYqh-. The loss of the Y chromosome was the sole karyotypic abnormality in nine patients, and the remaining four had additional chromosome changes. The peripheral blood lymphocytes were diploid in all except three cases, where no mitotic cells were recovered. The median age was 55 years, eight patients had acute myelogenous leukemia (M2) and five acute myelomonocytic leukemia (M4). Six patients (46%) had an antecedent hematologic disorder. Eleven patients received standard induction combination chemotherapy. Complete remission was achieved in seven patients (63%). Remission bone marrow chromosome analysis showed 100% 46,XY in all seven cases. The median durations of complete remission and survival were 10 months and 12 months, respectively. The review suggests that -Y is a consistent, although uncommon, chromosome marker in acute myelogenous leukemia, associated with an aggressive clinical course and intermediate prognosis.