481 cases of adult leukemia (115 acute lymphoblastic leukemia, ALL, and 366 acute nonlymphoid leukemia, ANLL) diagnosed at the Hematology Division of Pavia between 1976 and 1985 were reviewed to evaluate how many patients had an aplastic presentation. In 8 cases (1.6%) typical marrow hypoplasia preceded overt leukemia. At the leukemic transformation, the morphological and immunological findings were diagnostic for non-T non-B ALL in 2 cases, for ANLL in 5 cases (2 M1, 2 M2, 1 M5) and for Ph'-negative chronic granulocytic leukemia in 1 case. Median survival from the onset of leukemia was 5 months. In a certain proportion of cases aplastic anemia may be considered as a preleukemic state with a low propensity to develop into acute leukemia.