Expression of antigen CD 34+ on acute myeloid leukemia is admittedly regarded as a negative prognostic factor, however some authors deny it. The aim of our studies was clinical, morphological and immunological analysis of AML CD 34+. In the group of 39 patients with de novo AML there was 46% of AML CD 34+ (18 cases--14 women and 4 men aged 18 to 80 years--mean 52.5). The diagnosis was made according to FAB criteria and immunophenotype estimation by immunocytochemical method APAAP. The following types of AML were found: MO-4 cases, M1-1, M2-4, M4-8, M5-1. Analysis of clinical features of AML CD 34+ did not show any characteristic features either in peripheral blood smear, or bone marrow smear. Most patients were treated according to the EPR+Ara-C scheme, with addition of VP-16 in M4 types, one patient--IDA+VP-16 + Ara-C, three elderly patients were treated with low doses of Ara-c, one patient refused cytostatic treatment. Three patients achieved complete remission (17.6%), three achieved partial remission (17.6%), four died during the phase of aplasia and seven others (41.2%) were completely resistant for chemotherapy. These results confirm association between CD34 expression and drug resistance.