This paper reevaluates the recently reported excess mortality following transurethral resection of the prostate (TURP) for benign hypertrophy as compared with traditional open resection (OPEN). We studied survival through linkage of hospital discharge data with mortality data for the entire male population of Denmark (1977-85). For a maximum of 10.5 years 38,067 prostatectomy patients were followed. Adjusting for age and health status before surgery, TURP patients were subject to significantly higher levels of mortality than OPEN patients (RR = 1.19, 95% confidence interval (1.15-1.24). The extent to which this difference is attributable to the surgical intervention itself remains an open question. The two groups of patients are quite different with regard to age and preoperative health status, and available data may not be sufficient to control such differences through statistical analysis. On the other hand, the difference in mortality persisted over calendar time, even during periods when the pattern of utilization for the two procedures changed significantly (constant RR = 1.19, adjusting for age and comorbidity). The most important causes of death among Danish TURP patients differ from the causes suggested on the basis of previously reported Canadian data. The current evidence is thus ambiguous with regard to hypothetical biologic mechanisms behind the excess mortality over TURP patients. Further investigations are needed to evaluate the safety and effectiveness of prostate surgery.