One hundred patients undergoing vaginal surgery for genital prolapse were randomly allocated to one of four post-operative management groups which included a control group and three groups receiving differently acting pharmacological agents (distigmine bromide, phenoxybenzamine hydrochloride, and prostaglandin F2 alpha) variously reported as being useful in preventing urinary retention after vaginal surgery. The incidence of an elevated residual volume in the control group was 10.7%. All the pharmacological agents appeared to increase by about three times the incidence of an elevated residual urinary volume with statistical significance (P less than 0.05) being noted for distigmine bromide and PGF2 alpha. While this increased incidence occurred irrespective of the type of surgery in the case of distigmine bromide and phenoxybenzamine . HCl, the increase was most marked (P less than 0.01) when PGF2 alpha was used after anterior repair surgery.