Five elderly patients aged over 75 years with rectal prolapse were manometrically studied before and one year after Delorme's procedure with repair of the external anal sphincter (EAS) and puborectal muscle (PR), and compaired with 11 normal subjects (11 females, aged 61-76 years with a mean age of 68.9 years) as controls. All five patients who underwent Delorme's improvement operation were female aged 75-82 years with a mean of 78.9 years. They were strainer and multipara with occasional soiling. When studied one year after operation, three out of five patients (60%) had a small amount of soiling, and two patients (40%) had no soiling. In the anorectal manometry before operation, all of the patients showed significantly poor results in anal sphincter function, rectal sensory function, and rectal reservoir function compared with those of normal subjects (p<0.005, respectively). After the operation all of the patients showed significantly lower resting and squeezing pressure than that of normal subjects (p<0.05), but rectal sensory and reservoir functions were restored to normal. The results suggested that improvement of the rectal sensory and reservoir function by pulication of prolapsed wall of the rectum may contribute to the decrease and disappearence of soiling. Sphincter dysfunction may be due to injury to the EAS caused by delivery and long-time straining. Therefore, soiling may be improved by repair of the PR and not by repair of the EAS.