To investigate the immunophenotypic characteristics of multiple myeloma (MM) cells, 20 bone marrow samples from patients with multiple myeloma were analyzed by flow cytometry with three-color direct immunofluorescence staining. Results showed that all of myeloma cells expressed bright CD38, dim or negative CD45 and negative CD19. Most of the cells were CD56(+) and a small portions were ckappa(+) or clambda(+), or CD20(+). The phenotypes of normal plasmocyte, CD19(+) and CD56(-), except CD56(-) in one-third samples, were not appeared in all detected samples. It was concluded that the surface marker analysis of myeloma cells is a useful tool for diagnosis and further evaluating prognosis of multiple myeloma.