© The Author 2017; Published by Oxford University Press on behalf of the International Epidemiological Association all rights reserved. Background: Ovarian cancer incidence differs substantially by race/ethnicity, but the reasons for this are not well understood. Data were pooled from the African American Cancer Epidemiology Study (AACES) and 11 case-control studies in the Ovarian Cancer Association Consortium (OCAC) to examine racial/ethnic differences in epidemiological characteristics with suspected involvement in epithelial ovarian cancer (EOC) aetiology. Methods: We used multivariable logistic regression to estimate associations for 17 reproductive, hormonal and lifestyle characteristics and EOC risk by race/ethnicity among 10 924 women with invasive EOC (8918 Non-Hispanic Whites, 433 Hispanics, 911 Blacks, 662 Asian/Pacific Islanders) and 16 150 controls (13 619 Non-Hispanic Whites, 533 Hispanics, 1233 Blacks, 765 Asian/Pacific Islanders). Likelihood ratio tests were used to evaluate heterogeneity in the risk factor associations by race/ethnicity. Results: We observed statistically significant racial/ethnic heterogeneity for hysterectomy and EOC risk (P=0.008), where the largest odds ratio (OR) was observed in Black women [OR=1.64, 95% confidence interval (CI)=1.34-2.02] compared with other racial/ ethnic groups. Although not statistically significant, the associations for parity, firstdegree family history of ovarian or breast cancer, and endometriosis varied by race/ethnicity. Asian/Pacific Islanders had the greatest magnitude of association for parity (≥3 births: OR=0.38, 95% CI=0.28-0.54), and Black women had the largest ORs for family history (OR=1.77, 95% CI=1.42-2.21) and endometriosis (OR=2.42, 95% CI=1.65- 3.55). Conclusions: Although racial/ethnic heterogeneity was observed for hysterectomy, our findings support the validity of EOC risk factors across all racial/ethnic groups, and further suggest that any racial/ethnic population with a higher prevalence of a modifiable risk factor should be targeted to disseminate information about prevention.