A panel of eight antibodies was used by the alkaline-phosphatase/anti-alkaline phosphatase (APAAP) method to stain peripheral blood films, bone marrow smears, and cytocentrifuge preparations from 29 cases of acute myeloid leukemia. These findings were correlated with the French-American-British (FAB) classification. Leukemic cells from six cases of myeloblastic leukemia (FAB;M1) were predominantly labeled by the antimyeloperoxidase monoclonal antibody (MPO-7). Leukemic cells from the majority of eight cases of myeloblastic leukemia with maturation (FAB;M2) and progranulocytic leukemia (FAB;M3) stained with monoclonal antibodies MPO-7, NP57 (anti-elastase), and EBM11 (antimonocyte/macrophage). Leukemic cells from six cases of myelomonocytic (FAB;M4) and five cases of monocytic (FAB;M5) leukemia were most often labeled with antibodies MPO-7, NP57, and EBM11 as well as monoclonal antibodies Y1/82A (anti-monocyte) and KB90 (against the p150, 95 molecule, CD11c; a monocyte/granulocyte marker), but not with monoclonal antibody C17 (antiglycoprotein IIb/IIIa) and/or monoclonal antibody Y2/51 (antiglycoprotein IIIa). Erythroblasts from a single case of erythroleukemia (FAB;M6) were not labeled with any of the antibodies from this panel. Leukemic cells from two cases of acute megakaryocytic leukemia (FAB;M7) stained strongly with the monoclonal antiglycoprotein IIIa/IIb antibody (C17) and antiglycoprotein IIIa antibody (Y2/51). Staining by the APAAP method with this panel of antibodies was easy to perform, required no expensive instrumentation, and provided useful information in the classification of acute myeloid leukemia.