AIM:To investigate the therapeutic usefulness of leukocytapheresis (LCAP;Cellsoba) in steroid-naive patients with moderately active ulcerative colitis (UC).METHODS:Eighteen steroid-naive patients with moderately active UC received one LCAP session every week for five consecutive weeks.RESULTS:The remission rate 8 weeks after the last LCAP session was 61.1% (11/18).All three patients with deep ulcers showed worsening after LCAP.For the remaining 15 patients,who had erosions or geographic ulcers,the average clinical activity index (CAI) score dropped significantly from 9.4 to 3.8eight weeks after the last LCAP session (t=4.89,P=0.001).The average C-reactive protein (CRP) levels before and after LCAP were 1.2 mg/dL and 1.0 mg/dL,respectively.Of the patients with erosions,geographic ulcers,and deep ulcers,100% (9/9),33.3% (2/6),and 0% (0/3) were in remission 8 weeks after the last LCAP session,respectively (x2=7.65,P < 0.005).Fortyeight weeks after the last LCAP session,the remission rates for patients with erosions and geographic ulcers were 44.4% (4/9) and 16.7% (1/6),respectively.Only one patient suffered a mild adverse event after LCAP (nausea).CONCLUSION:LCAP is a useful and safe therapy for steroid-naive UC patients with moderate disease activity.Moreover,the efficacy of the treatment can be predicted on the basis of endoscopic findings.