AIM: To determine the expression level of Fas molecules on the T cells isolated from systemic lupus erythematosus (SLE) patients. METHODS: The expression of Fas on T cells and the apoptotic rate of 36 patients with SLE in active phase and 18 normal people were determined with flow cytometry. The patients were treated with impact therapy of prednisone, methylprednisolone or cyclophosphamide, respectively, according to their conditions. Within 3 days after admission, immediately before discharging (the average days in hospital is 22.6 d), and 4 weeks after discharging, the amount of Fas molecules expressed on T cell surface was determined respectively with flow cytometry in each patient. RESULTS: There was a positive correlation between SLEDAI, apoptotic rate of T cells and Fas molecules on T cells in SLE patients of active phase (P