Clinical function and anorectal physiological function were assessed and correlated in 20 patients with ulcerative colitis before restorative proctocolectomy and 3, 7, and 12 months after operation. The entire anal sphincter was preserved by means of a stapled pouch-anal anastomosis. Before operation, the median resting anal pressure was 79 cmH2O (interquartile range 70-89 cmH2O), the rectoanal inhibitory reflex was present in all patients and anorectal 'sampling' was noted in 16 of 20 patients. Three months after operation, resting anal pressure was 68 cmH2O (range 50-87 cmH2O) (P less than 0.001), the reflex was present in only three patients (P less than 0.001) and sampling was observed in one patient. After 7 months, resting anal pressure was 76 cmH2O (range 64-89 cmH2O), the reflex was present in 11 patients and sampling was observed in nine patients. At 12 months, resting anal pressure was 84 cmH2O (range 66-94 cmH2O), the reflex was present in 19 patients and sampling was observed in 17 patients. The compliance and capacity of the reservoir increased significantly. Ability to discriminate flatus from faeces was associated with return of the rectoanal reflex and sampling.