Current long-term treatment of Crohn's disease is unsatisfactory. Based on the Crohn's Disease Activity Index (CDAI), this multicenter trial enrolled patients with either active Crohn's disease (CDAI > or = 150) or disease in remission (CDAI < 150). The primary measure of therapeutic response was mean change in CDAI from baseline to final visit. All patients began treatment with a dosage of < or = 4 g/day of mesalamine that ranged from 3.7 g at baseline to 3.4 g at final visit. Overall, 467 patients were enrolled: 333 (active disease) and 134 (remission). The median study participation time was 14 months. For patients entering with active disease, the mean reduction in CDAI was 77 points, with 42% (122/289) achieving remission by their final visit. For patients entering in remission, there was an increase in mean CDAI from 90 at baseline to 96 at final visit, with 79% (95/120) of patients in remission at final visit and 72% (31/43) in remission continuously after 12 months of therapy. From baseline to final visit, the mean prednisone dose decreased 5 mg/day in patients with active disease and 11 mg/day in patients in remission. Mesalamine was well tolerated and no adverse laboratory trends were observed. These results suggest that controlled-release mesalamine shows promise as a steroid-sparing agent and as a safe and effective long-term therapy for the induction of and maintenance of remission of mild-to-moderate Crohn's disease.