OBJECTIVE: This study examined the relationship of clinicopathologic, health status, medical system, and socioeconomic factors to differences in stage at diagnosis of endometrial cancer in black and white patients. STUDY DESIGN: A population-based study of 130 black and 329 white patients with invasive endometrial cancer was conducted as part of the National Cancer Institute's Black/White Cancer Survival Study. Logistic regression was used to determine the relative importance of factors thought to be related to stage at diagnosis after age and geographic location were adjusted for. RESULTS: High-grade (poorly differentiated) lesions increased the risk for stage III or IV disease (odds ratio 8.3, 95% confidence interval 3.4 to 20.3), as did serous histologic subtype (odds ratio 3.5, 95% confidence interval 1.4 to 8.8) and no usual source of care (odds ratio 5.5, 95% confidence interval 1.4 to 20.9). In the final statistical model these three factors also accounted for the majority of the excess risk of advanced stage for blacks. CONCLUSIONS: Black-white racial disparities in stage at diagnosis appear to be related to higher-grade lesions and more aggressive histologic subtypes occurring more frequently in black patients with endometrial cancer.