To evaluate patterns of practice and outcomes in intermediate- and high-risk stage I and II endometrial cancer in the province of Ontario, Canada. This was a retrospective population-based study of women diagnosed with stage I and II endometrial cancer in Ontario from 1996 to 2000. After excluding low-risk (stages IA and IB, grades 1 and 2) and nonendometrioid histologies, the population was stratified into two risk groups: intermediate risk (stages IA and IB, grade 3; stages IC and IIA, grades 1 and 2; stage IIA, grade 3 if <50% myometrial invasion) and high risk (stage IC, grade 3; stage IIA, grade 3 if >50% myometrial invasion, and all stage IIB). Patterns of practice were assessed in each risk group, including use of surgical staging and adjuvant pelvic radiotherapy (APRT). Cox proportional hazards models determined effects of prognostic factors on 5-year overall survival (OS), including age, income, comorbidities, lymphvascular space invasion (LVSI), surgical staging, and APRT. There were 995 women in this study: 748 intermediate risk (75.2%) and 247 high risk (24.8%). Only 69 (9.2%) and 40 (16.2%) women underwent surgical staging in the intermediate- and high-risk groups, respectively. Surgical staging did not reduce rates of APRT. Determinants of survival included age >60 and comorbidities in the intermediate-risk group, and age >60, income, and LVSI in the high-risk group. In this population-based study, there were variable patterns of practice for intermediate- and high-risk stage I and II endometrial cancer. Surgical staging and APRT did not affect OS.