The aim of the study was to evaluate the efficacy of 5-aminosalicylic acid (5-ASA) in maintaining the remission in patients with inactive Crohn's disease over a period of three years, using either the Crohn's Disease Activity Index (CDAI) and or the Laboratory Index (LI). Thirty-eight patients entered in the study; 20 received 5-ASA 1.6 g/day and 18 no specific therapy. The patients were followed for three years. Of the patients, 86% presented a relapse, 80% in the 5-ASA group and 94% in the control group. Two patients requested surgical therapy. All patients with clinical relapse had CDAI greater than 150 and LI greater than 100. 5-Aminosalicylic acid was well tolerated and was able to protect from relapse up to 60% of the patients in the first year of therapy. When treatment with 5-ASA is prolonged for periods longer than one year a progressive increase in the number of patients who present relapse can be observed, but of the 5-ASA group, 80% of relapses occurred in the three years whereas the control group showed 94% relapses at the end of the first year.