SUMMARYEight patients with AML of unfavourable prognosis were treated with combinations of low doses of ara‐C, retinoic acid, vitamin D3 and alpha‐interferon. 2 complete remissions and 3 partial responses were achieved. The good response in this patient group, together with the observation that 3 of the responders (1 complete remission) had no prior marrow hypoplasia, are suggestive of mechanisms of action that are separate from those in conventional chemotherapy. Possible alternatives are the induction of differentiation of leukemic cells, stimulation of normal stem cells, a slowly active selective cytotoxicity on leukemic stem cells with only minor side effects on normal stem cells, or combinations of these mechani