5-aminosalicylic acid (5-ASA) is known to be effective in the treatment of active ulcerative colitis (UC). The aim of the current study was to investigate the effect of 5-ASA enemas, as a maintenance therapy for UC, when administered twice weekly as a weekend treatment regimen, compared to daily oral 5-ASA alone. We hypothesized that the weekend enema therapy would be better tolerated by patients who worked or attended school.Between January 2004 and August 2005, patients with UC, in whom remission of the condition had just been induced, were randomly assigned to either: the weekend 5-ASA enema group (n=11), who received 1 g 5-ASA enemas twice a week on Saturday and Sunday plus oral 5-ASA 3 g/day for 7 days, or to the daily oral 5-ASA use only group (n=13), who received only oral 5-ASA 3 g/day for 7 days. The primary endpoint of the study was defined as the incidence of relapse. The study was stopped after 24 patients had been enrolled because an interim analysis showed a significant benefit of the weekend 5-ASA enema group.In the weekend enema group, 2 patients (18.2%) had relapses compared with 10 (76.9%) in the oral 5-ASA only group. The multivariate hazard ratio of relapse associated with weekend 5-ASA enema, relative to the oral alone group, was 0.19 (95% confidence interval, 0.04-0.94).This study demonstrated the beneficial effects of adding weekend 1 g 5-ASA enema to daily 3 g oral 5-ASA as maintenance therapy for UC.