Dr. SENN supposed that in Dr. NAJEAN’s series certain cases are included which others (according to common AML-study criteria) would have treated as overt acute myeloid leukemia. These patients would have had a 50%-60% chance of complete remission, but they were treated with androgens or low doses of cytosine-arabinoside. In the second trial, similar cases were eliminated by waiting 3 months; some patients, which had already had frank acute leukemia, may have been lost by not treating them. Dr. NAJEAN answered that none of the patients had more than 40% blasts in the bone marrow, nor myeloblastosis in the peripheral blood. When the myeloblasts amounted to more than 40% the patients were excluded from the protocol and treated by chemotherapy as used in acute myeloblasts leukemia. A fourth of them died very quickly, and only one of the complete remissions out of sixty patients treated by heavy chemotherapy enjoyed long-lasting survival (over 12 months). In Dr. HEIMPEL’s series, only 20% of the patients had a survival time of more than 60 months, although none of them entered complete remission. To the problem of androgens, Dr. HEIMPEL stated that, comparable to the situation in aplastic anemia, some patients with preleukemia respond to androgen therapy. Therefore, one should give these patients a chance of treatment with androgens. Chemotherapy of acute leukemias at a stage when there is only a small fraction of blast cells, is probably as successful as in leukemias with higher blast counts. It is essential to have an observation period of possibly 3 months, because it is not so much the low proportion of leukemic cells, as the low in-crease of leukemic cells, which distinguishes this group from a group of usual acute leukemias.