Recently, young people with chronic ulcerative colitis and familial polyposis have been undergoing colectomy with rectal mucosectomy and ileoanal anastomosis with encouraging clinical results. However, during the early period after closing the temporary ileostomy, some patients have frequent stools, which decrease with time as the terminal ileum dilates and becomes a reservoir. To enhance the early development of the neorectal reservoir and to minimize the frequent stooling, we instituted balloon dilations of the neorectum before ileostomy closure. A group of 16 patients not undergoing balloon dilations were compared with a similar group of 13 patients who had balloon dilations. Patients undergoing balloon dilations were observed to have an increase of 40.6% per month in the measured volume of the neorectum, along with a decrease of approximately 40% in the mean number of stools at 3 mo and 34% at 6 mo, with a very acceptable clinical result.