Expression of erythroid antigens identifying with the use of monoclonal antibodies (mab) HAE3 and HAE9 was studied in 333 patients with different types of hemoblastoses. Frequency of erythroid variants based on the reaction with mab was 5.7%. In 2.4% of cases erythroid markers were the only indication on the nature of leukemia. In 2.7% of cases the types of leukemia were accounted for as "mixed" ones, i.e. erythrolymphoid and erythromyeloid variants. Only in 0.6% of cases erythroid variant was detected by the morphological criteria.