Early postoperative mortality following hysterectomy. A Danish population based study, 1977-1981. The main objective of this cohort study was to analyse the early postoperative mortality after 'simple' hysterectomy for benign indications and to compare it with that of a randomly selected reference group of women matched for age. Registry data covering the entire Danish female population were used. Included in the study were all patients operated in the period 1977-1981. Patients were only included if no cancer was diagnosed and if no major co-surgery was performed (29,192 patients). Cancer patients were also excluded in the reference group (16,182 women). Mortality was studied according to characteristics of patients, their residential area, the surgical approach and operating hospital. Overall 47 patients died within 30 days of admission for hysterectomy (overall mortality 16.1 per 10,000). Only seven deaths were expected on the basis of the population sample, and adjusted for age, the relative risk (RR) for hysterectomy patients was 6.38 (95% CI 4.33-9.39). Early postoperative mortality increased with age, and the risk was elevated among emergency patients (RR = 3.22; 1.72-6.04). Patients with more than one diagnosis at discharge (RR = 4.53; 2.12-9.70) were at high risk, but early postoperative mortality was independent of surgical approach. Causes of death are discussed. Compared to the general population, patients who undergo 'simple' hysterectomy are faced with a sixfold risk of dying within 30 days, but a complete assessment of the risks and benefits of hysterectomy requires prospective studies of survival and morbidity, including quality of life for longer periods of time following operations. 