Objective: To examine the association of maternal and paternal ethnicity as well as parental ethnic discordance with preeclampsia. Methods: Retrospective cohort study of all low-risk women delivered from 1995 to 1999 within a mature managed care organization. Rates of preeclampsia were calculated for maternal, paternal, and combined ethnicity using both univariate and multivariate analyses. Results: Among the 127,544 low-risk women, when examining maternal ethnicity in a multivariate model controlling for maternal age, parity, education, and gestational age, we found that the rates of preeclampsia were higher among African American (5.2% ; odds ratio OR 1.41, 95% confidence interval CI 1.25-1.62) women and lower among Latina (4.0% ; OR 0.90, 95% CI 0.84-0.97) and Asian women (3.5% ; OR 0.79, 95% CI 0.72-0.88), with all results being statistically significant as compared with white women. When paternal ethnicity was controlled for separately, however, the difference in the rate of preeclampsia among Asian women disappeared, the effect of African-American maternal ethnicity increased slightly (OR 1.49, 95% CI 1.33-1.72), and Asian paternity was found to be associated with the lowest rate of preeclampsia (3.2% ; OR 0.76, 95% CI 0.68-0.85). Further, parental ethnic discordance was associated with an increase in the rate of preeclampsia (OR 1.13, 95% CI 1.02-1.26). Conclusion: We found that rates of preeclampsia were lower with Asian paternal ethnicity. We also found that having a differing paternal and maternal ethnicity was associated with increased rates of preeclampsia. For every 1,000 pregnancies, there would be approximately 10 fewer cases of preeclampsia in the setting of Asian paternity and 5 more cases of preeclampsia in the setting of parental ethnic discordance. These differences may be useful in further investigation of the cause of preeclampsia. Objective: To examine the association of maternal and paternal ethnicity as well as parental ethnic discordance with preeclampsia. Methods: Retrospective cohort study of all low-risk women delivered from 1995 to 1999 within a mature managed care organization. Rates of preeclampsia were calculated for maternal , paternal, and combined ethnicity using both univariate and multivariate analyzes. Results: Among the 127,544 low-risk women, when examining maternal ethnicity in a multivariate model controlling for maternal age, parity, education, and gestational age, we found that the rates of preeclampsia were higher among African American (5.2%; odds ratio OR 1.41, 95% confidence interval CI 1.25-1.62) women and lower among Latina (4.0%; OR 0.90, 95% CI 0.84-0.97) and Asian women OR 0.79, 95% CI 0.72-0.88), with all results being presented significant statistically compared with white women. When paternal ethnicity was controlled separately, however, the difference in the rate of preec lampsia among Asian women disappeared, the effect of African-American maternal ethnicity greatly increased (OR 1.49, 95% CI 1.33-1.72), and Asian paternity was found associated with the lowest rate of preeclampsia (3.2%; OR 0.76, 95 %, CI 0.68-0.85). Further, parental ethnic discordance was associated with an increase in the rate of preeclampsia (OR 1.13, 95% CI 1.02-1.26). Conclusion: We found that rates of preeclampsia were lower with Asian paternal ethnicity. We also found that having a differing paternal and maternal ethnicity was associated with increased rates of preeclampsia. For every 1,000 pregnancies, there would be approximately 10 fewer cases of preeclampsia in the setting of Asian paternity and 5 more cases of preeclampsia in the setting of parental ethnic discordance. These differences may be useful in further investigation of the cause of preeclampsia.