The karyotype 47,XX, + 8,t(12;22)(p13;q12) was found at diagnosis in two patients with acute nonlymphocytic leukemia (ANLL). The bone marrow morphology of both patients corresponded to the M4 subtype of the French-American-British (FAB) classification. The translocation t(12;22) has not previously been reported as the sole structural aberration in ANLL.