The aim was to study the morphological, histochemical and immunological characteristics of less-differentiated acute myeloid leukemic cells, and their diagnostic significance. Wright-Giemsa and histochemical staining were used to stain bone marrow smears from 2 case of AML-Mo. Immunological phenotypes were determined with flow cytometry. The results showed that myeloperoxidase stainings of both cases were negative, PAS was positive with fine particles, CD33/CD13 were positive, CD2/CD3/CD10/CD19/CD22 were negative. It is concluded that morphology, histochemistry and immunological phenotype on bone marrow smears are the main diagnostic basis for AML-Mo. The use of multiple monoclonal antibodies for staining may improve the accuracy.