Few data are available about the clinical course of severe colonic Crohn's disease (CD). The aim of this study is to desrcibe the clinical course of severe Crohn's colitis in a patients cohort with isolated colonic or ileo-colonic CD and to compare it with the clinical course of patients with severe ulcerative colitis (UC). Thirthy-four patients with severe Crohn's colitis were prospectively identified in our cohort of 593 consecutive hospitalized patients through evaluation of the Crohn's Disease Activity Index score and the Harvey-Bradshaw Index. One undred sixty-nine patients with severe ulcerative colitis were prospectively identified in our cohort of 449 consecutive hospitalized patients through evaluation of the Lichtiger score and the Truelove-Witts score. We evaluated the following data/aspects: response to steroids, response to biologies, colectomy rate in acute, colectomy rate during follow-up, megacolon and cytomegalovirus infection rate. We did not find significant differences in the response to stertoids and to biologies, in the percentage of cytomegalovirus infection and of megacolon, while the rate of colectomy in acute turned out be greater in patients with severe Crohn's colitis compared to patients with severe UC, and this difference appeared to be limit of statistical significance (chi-squared 3.31,p=0.069, OR 0.39); the differenc between the colectomy rates at the end of the follow-up also not significant. In the whole population, by univariate analysis, according to the luinear regression model a young age at diagnosis is associated with a higher overall colectomy rate (p=0.024) and a higher elective colectomy rate (p=0.022), but not with a higher acute colectomy rate, and an elevated ESR is correlated with a higher overall colectomy rate (p = 0.014) and a higher acute colectomy rate (p = 0.032), but not with a higher elective colectomy rate. This correlation was significant on multivariate analysis. The overall rate of colectomy in the cohort of patients with severe Crohn’s colitis was greater than that of the cohort of patients with severe UC, but this figure is not supported by a different clinical response to steroid therapy or rescue therapy with biologics. The clinical course of severe Crohn’s colitis requires to be clarified by prospective studies that include a larger number of patients in this subgroup of disease.