The aim of this study was to determine whether anorectal manometry could predict clinical outcome after closure of a diverting ileostomy made at the time of colectomy, mucosal proctectomy and endorectal ileoanal anastomosis for chronic ulcerative colitis. Twenty-two patients were studied, 6 with ileoanal anastomosis and 16 with ileal pouch-anal anastomosis. Resting anal sphincter pressures and pressure-volume curves (compliance) of the neorectum were assessed before the diverting ileostomy was closed and results were correlated with frequency and leakage of stools 1 month after closure. Before stomal closure, the mean (+/- standard error of the mean) resting sphincteric pressure was 44 +/- 5 cm H2O, while neorectal compliance was 2.3 +/- 0.3 ml/cm H2O. One month later daily stool frequency was 12 +/- 1, while severe leakage occurred in four patients during the day and in eight at night. The greater the sphincteric pressure and the compliance, the fewer were the number of stools per day (p less than 0.01). When pressure and compliance were considered together as an index of anorectal function, the correlation of stool frequency and leakage was even stronger (p less than 0.001). The authors conclude that anorectal manometry can predict early clinical outcome after ileoanal anastomosis.