To study the feasibility of using MTT assay to detect cell apoptosis.K562 cells were grown in RPMI 1640 medium supplemented with 10% calf serum and 4 micromol/L arsenic trioxide. Apoptosis was induced in the cultured cells by As2O3, and the cells were detected with optical microscope, DNA gel electrophoresis and MTT staining respectively.MTT staining could also accurately detect cell apoptosis, by which the apoptotic cells were easily distinguished from normal cells and dead cells.MTT staining is simple, convenient and practical for detecting cell apoptosis.