Erythroid and/or megakaryocytic dysplasia (EMD) was evaluated in diagnostic bone marrow smears of 37 consecutively treated cases with de novo acute myeloid leukemia (AML) M0-M2 and M4-M5 types and three newly diagnosed cases of refractory anaemia with excess of blasts in transformation. This evaluation was possible in 38 of 40 (95%) patients and 17 cases were categorized without EMD and 21 cases with EMD. One or two cycles with 3-4 doses of daunorubicin 45 mg/m2/d and cytosine arabinoside 200 mg/m2/12 h x 14 lead to complete remission in 13 of 16 cases without EMD but only in 4 of 16 cases with EMD (p = 0.004). However, 10 of 13 patients with EMD reached complete remission with 2000 mg/m2/12 h x 10 of cytosine arabinoside plus daunorubicin. After intensive consolidations 20 patients under 65 years with EMD showed significantly worse overall survival (p = 0.017) with a median 11.5 months, while the median survival was estimated 66.8 months in 15 cases under 65 years without EMD. The proposed categorization of de novo AML patients according to the EMD seems to be useful for selection of optimal induction therapy, clinically relevant for survival and might reflect two biologic groups of AML arising in two different stages of differentiation.