The potential for specific immunophenotypic characterization of the acute leukemias has been enhanced greatly by the development of monoclonal antibodies. Currently, this immunologic data is obtained most commonly by flow cytometric analysis or cellular cytotoxicity assays. The former is an expensive technic that lacks morphologic evaluation unless cell sorting is performed. The latter precludes morphologic assessment by the nature of the assay. The authors have developed an immunostaining procedure utilizing cytospin preparations and immunoperoxidase methods that are relatively inexpensive and allow simultaneous assessment of the immunologic markers and cellular morphology. Although a comparison of flow cytometry and immunocytology revealed quantitative differences for individual cell surface markers, the "qualitative" immunologic phenotype of the leukemic population was virtually identical by the two technics.