The authors analyse the short-term prognosis of ulcerative colitis from a series of 65 patients followed during ten years and treated with the same attitude. The results are compared to those of the most important published, from which they differ just a little. The medical treatment is effective in 84,6% of cases. The mortality of first attack is 6,1%. Only 1,4% of patients in our series are colectomised. It seems that the short-term prognosis has been slightly better during the last few years perhaps because of improvement in management and appearance of corticosteroids and/or salazosulfapyridine. The factors of bad prognosis in a first attack are its severity, its extension to the whole colon, its beginning after 60 years.