The elastic properties of the rectal wall have been studied in 16 normal adults (group I) and in 24 patients with ulcerative colitis, during a nonactive (13 cases, group II) or an active period (11 cases, group III). The rectal intraluminal pressures after accommodation to the distension were significantly higher in group III than in groups I and II. These pressures were not related to distending volumes in groups I and II but were correlated with the distending volumes in group III. The rectal elasticity coefficient was significantly greater in group III than in the other two groups. There was an inverse correlation between the rectal elasticity coefficient and the rectal area. These results suggest a loss of the rectal distensibility in active colitis.