Ileal pouch function in 35 patients operated upon by the same surgeon were compared. Seventeen of the patients had a double loop (J) ileal pouch-anal anastomosis (IPAA) and 18 a triple loop (S) pouch. The patients were examined a mean of 27.9 months and 5.1 months, respectively, after ileostomy closure. Ten of the S-pouch patients were evaluated more than 6 months (S greater than 6 months), mean 9.1 after ileostomy closure. There were no differences in the mean maximum resting pressures or maximum squeeze pressures between the groups. The incidence of daytime and nocturnal leakage was lower in the S-pouch group, 22 and 29 percent, than in the J group 29, and 53 percent. Though the mean maximum tolerated volume (MTV) of the S-pouch group was greater than the J group, the difference was not statistically significant. The difference in the mean compliance between the J- and S-pouch groups and the J and S greater than 6 months group was statistically significant (P less than 0.01) and (P less than 0.008). All the patients could evacuate spontaneously. The difference in the 24-hour frequency of defecation between the S greater than 6 months and J group was significant (P less than 0.05), but not between the S and J groups. The median frequency of nocturnal defecation between the S greater than 6 months and J pouch groups was significant (P less than 0.005), but not between the S and J groups. The triple loop S-pouches were more compliant than the J-pouches and had a better functional result as shown by a lower incidence of nocturnal leakage, and a lower frequency of defecation during the day and night.