The aim of this study was to determine whether tripterine, isolated from Tripterygium wilfordii Hoog f. in China, had beneficial effects on experimental systemic lupus erythematosus induced by active chromatin in BALB/c mice. BALB/c mice were immunized with active chromatin isolated from concanavalin A-activated syngenetic spleno-lymphocytes on day 0. Tripterine 6 or 12 mg kg(-1) day(-1), or prednisone 5 mg kg(-1) day(-1) was given to BALB/c mice intragastrically from day 35 to day 50. Treatment with tripterine 12 mg kg(-1) day(-1) for 15 days protected renal from glomerular injury with a concomitant reduction of serum autoantibodies and total immunoglobulin G (IgG) also with a improvement of splenocyte proliferation stimulated with concanavalin A and lipopolysaccharide. The effects were associated with reduced interleukin-10 production and serum nitric oxide (NO) level but not interferon-gamma compared with vehicle-treated control group. Tripterine 6 mg kg(-1) day(-1) had no significant protective effect against glomerular injury. It inhibited autoantibodies and interleukin-10 production but had no effect on splenocyte proliferation, serum NO level, and interferon-gamma production. These findings suggested that tripterine had a beneficial effect on systemic lupus erythematosus induced by active chromatin in BALB/c mice.