The technique of proctocolectomy and formation of an ileal reservoir with ileoanal anastomosis is well described. It is believed that the conservation of a rectal muscular cuff is necessary for continence but no data are available to support this contention. The aims of this study were to describe the clinical and physiological aspects of continence after proctocolectomy and ileal J pouch anastomosis without conservation of a rectal muscular cuff. Eighteen consecutive patients (mean age 37.3 years, 16 ulcerative colitis, two familial polyposis) who underwent proctocolectomy and ileoanal anastomosis on the dentate line were studied 6 months after closure of the loop ileostomy. The 18 patients and eight controls underwent: (a) anal manometry; (b) determination of maximum tolerable volume (MTV); (c) liquid continence test (infusion of NaCl at 60 ml/min for 25 min) with simultaneous measurement of ileal reservoir pressure. The volume evacuated during 5 min after the continence test was also measured. The frequency of bowel actions was (mean +/- s.e.m.) 5.3 +/- 0.4 per 24 h (nocturnal 1.14 +/- 0.26). Seventeen of 18 patients (94 per cent) had normal continence and defaecation; one patient was incontinent. A decrease in resting anal canal pressure (102.5 +/- 4 versus 47.5 +/- 6 cmH2O) was observed after ileoanal anastomosis. A rectoanal inhibitory reflex was elicited in one of the 18 patients (6 per cent). Patients were able to retain 1023 +/- 68 ml saline during the liquid continence test. The percentage evacuation of the ileal reservoir was 61 +/- 4.5 per cent. Correlations were found (P = 0.05) between daily stool frequency and the volume of saline retained during the liquid continence test. It is concluded that conservation of a rectal muscular cuff is not necessary for the achievement of good clinical results.