[en] INTRODUCTION: Mesalazine remains the first line treatment for the induction and the maintenance of remission in mild to moderate ulcerative colitis (UC). Its efficacy as a maintenance treatment after a first flare treated with corticosteroids has not been specifically studied. The aims of our work were to study a cohort of UC patients treated with mesalazine after a course of oral systemic corticosteroids and to identify predictive factors of relapse and of colectomy. MATERIAL AND METHOD: We studied retrospectively a cohort of 143 UC patients, who never received immunosuppressive drugs, and treated for the first time with oral corticosteroids for a flare. Among patients responding to corticosteroids, we studied the group treated by mesalazine after the flare. RESULTS: Fifty% (n=52) achieved a complete clinical remission with steroid weaning. In this group, 67% (n=35) received oral mesalazine. Seventy-five % of patients treated by mesalazine relapsed (median 29 months, range: 1-156). Fourteen % required a colectomy (median 11 months, range: 1-24). Kaplan Meier curve showed a relapse rate and a colectomy rate over one year of 26% and 11% respectively. In multivariate analysis, male gender and short duration of disease were predictive factors of the time-to-relapse. No factor was predictive of time-to-colectomy. CONCLUSION: Maintenance efficacy of mesalazine over one year after a first course of corticosteroids for a disease flare is reasonably high. The longer-term relapse rate becomes higher in male patients with a short disease duration. An immunosuppressive treatment could be discussed in case of further relapse despite improved medication-adherence. Medication-adherence should first be assessed and promoted. An immunosuppressive treatment could be discussed in case of further relapse despite improved medication-adherence.