We conducted a pilot study to investigate whether tacrolimus was effective for treating patients with systemic lupus erythematosus (SLE) without renal involvement. Ten SLE patients with symptoms such as arthritis and erythema, but no active nephritis, were treated with tacrolimus. They included 8 women and 2 men aged from 24 to 62 years [mean +/- standard deviation (SD): 42.1 +/- 11.3 years]. Tacrolimus was administered at doses of 1-3 mg daily, and efficacy was assessed from the SLE Disease Activity Index (SLEDAI) after 1 year. Two patients ceased treatment due to adverse reactions (after 4 days for chest pain and 7 months for recurrent infections). The other 8 patients completed 1 year of treatment, and significant improvement of disease activity was observed in 6 of them. The mean (+/-SD) SLEDAI showed a significant decrease after 1 year of tacrolimus therapy, from 6.8 +/- 3.1 to 3.4 +/- 0.9; p < 0.05 by Student's paired t test. The mean (+/-SD) dose of prednisolone also decreased significantly, from 16.8 +/- 8.6 to 9.3 +/- 4.6 mg/day; p < 0.05. Although a prospective controlled study will be necessary to confirm, tacrolimus might be a treatment option for active SLE without renal involvement.