Endometrial carcinoma (EC) is the most common extracolonic tumor associated with hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC increases the risk of EC compared to the general population. Patients with HNPCC have a better prognosis than patients with common sporadic colorectal cancer. It is unknown, however, whether the survival rate of HNPCC-associated EC is higher than that of sporadic EC. The aim of our study was to compare the survival rates of HNPCC-associated EC with sporadic EC. From the registry of the Netherlands Foundation for Hereditary Tumors, 50 patients with HNPCC-associated EC from 46 families harboring a germline mutation or fulfilling the Amsterdam Criteria II were age-and stage-matched with 100 patients with sporadic EC registered in the Eindhoven Cancer Registry in the Netherlands. Survival rates were analyzed. The overall 5-year cumulative survival rates for patients with HNPCC-associated EC was 88% and 82% for patients with sporadic EC (p ‫؍‬ 0.59). In Stages IA, IB and IC, the survival rates of patients with HNPCC-associated EC and sporadic EC were 92% and 91%, respectively (p ‫؍‬ 0.90). In Stages IIIA and IIIC, the survival rates for HNPCC-associated EC and sporadic EC were 72% and 50%, respectively (p ‫؍‬ 0.38). Furthermore, there was no significant difference in the distribution of tumor histologic subtypes in the study and control groups (p ‫؍‬ 0.55). The outcomes in survival in EC in the general population and in women from families with HNPCC do not differ significantly. These results may have important implications in our understanding of EC and the role of early screening. © 2002 Wiley-Liss, Inc. Key words: survival; hereditary nonpolyposis colorectal cancer; endometrial carcinoma; case-control studyEndometrial carcinoma (EC) is the most common genital malignancy in women occurring with a cumulative lifetime risk of approximately 1.5-3%. 1,2 Predominantly a disease of postmenopausal women, EC presents at a median age at diagnosis of 63 years. 3 Risk factors associated with EC include unopposed estrogen use, obesity, late menopause, early menarche, nulliparity, hypertension, diabetes mellitus and hereditary tumor syndromes. 4,5 An estimated 5% of all cases of EC is associated with a hereditary cause. 6 Hereditary nonpolyposis colorectal cancer (HNPCC), an autosomal dominant cancer syndrome, is caused by a germline mutation in DNA mismatch repair (MMR) genes, most frequently in MLH1, MSH2 and MSH6. 7 These mutations predispose to cancer of the colorectum and endometrium, most commonly, and to cancers of various other locations such as the stomach, upper urinary tract, ovaries and small bowel. 8 The cumulative incidence of HNPCC-associated EC is approximately 20% by age 70. 2 Some MMR mutations in female carriers increase the risk of EC to 40 -50%. 9 -12 Improved survival has been reported in HNPCC-associated colorectal cancer (CRC) as compared to sporadic CRC of an equivalent stage. 13 The 5-year cumulative survival rate of CRC associated with MLH1-mutations is 65% in co...