Multiphenotypic acute leukemias (MAL), defined by the coexpression on most blast cells of antigens classically attributed to different lineages, remain a rare event. We isolated a series of 26 such cases from a cohort of 1565 leukemic patients whose cells were immunophenotyped at diagnosis. Markers of B and myeloid lineage (BM) were associated in 16 cases (62%), 3 coexpressed B and T markers (BT), and T-cell and myeloid antigens (TM) were found in 7 (27%). A tumoral syndrome was observed in 69% of the patients, without significant differences between the immunophenotypic subgroups. Median event free survivals in the three immunophenotypic subgroups as defined were respectively 24 months for BM-MAL, 4 months for TM-MAL and 7 months for BT-MAL respectively. The poorer prognosis of TM-MAL was significantly different from that of BM-MAL (p < 0.001). This concurred with the poorer prognosis associated with CD7 expression or absence or CD10, both characteristic features of TM-MAL.