Previous studies using large administrative databases found an elevated relative risk of reoperation and death after transurethral resection of the prostate compared to open prostatectomy. To investigate whether differences in case-mix unmeasured by administrative data explained this finding, we reviewed the charts of 485 patients who had undergone prostatectomy (236 open and 249 transurethral) at the Health Science Centre, Winnipeg, Manitoba, Canada between 1974 and 1980. Data from patient histories, physical examinations and laboratory evaluations were abstracted and used to control for case-mix in models comparing the rates of reoperation and mortality after transurethral versus open prostatectomy. Several models were specified. In all models the relative risk of dying after transurethral prostatectomy remained elevated (1.36 to 1.89), as did the risk for reoperation (3.62). A prospective trial is needed to establish the relative safety and effectiveness of transurethral and open prostatectomy.