Intercurrent mortality and the pattern of inpatient hospital care was studied among 1,846 postmenopausal patients included in the Stockholm randomized trial of adjuvant tamoxifen (40 mg daily for 2 years) versus no adjuvant endocrine therapy. The median follow-up time was 54 months (range, 2 to 123 months). The patients were matched to the Swedish National Registry of Causes of Death and a computerized register covering about 95% of all hospital admissions in Stockholm County. There was no significant difference in the pattern of intercurrent mortality among the tamoxifen and control patients. The total number of hospital admissions was similar in both groups, but the tamoxifen patients were admitted significantly less frequently because of immunologic diseases (relative risk [RR] = 0.4; 95% confidence interval [CI], 0.2 to 0.9). Admissions because of thrombotic diseases were slightly, but not significantly, more frequent among the tamoxifen patients (RR = 1.2; 95% [CI], 0.6 to 2.3). The risk of hospital stay for benign gynecologic diseases other than prolapse or uterine bleeding was increased in the tamoxifen group (RR = 3.2; 95% CI, 1.2 to 8.6). No significant differences were found for diseases related to arteriosclerosis or osteoporosis. The study confirms and extends previous reports, which have shown that tamoxifen has few and usually mild side effects. However, the current results should be judged cautiously because of the relatively short median follow-up time (4.5 years) and the limitation of data in detecting morbidity that does not necessarily result in hospitalization.