Objective: Trans fatty acids, formed by the partial hydrogenation of vegetable oils, are associated with increases in plasma concentrations of cholesterol, triglyceride, lipoprotein (a), and coronary heart disease risk. Trans fatty acids may also increase platelet aggregation and alter eicosanoid biosynthesis. We studied the relation between maternal dietary intake of trans fatty acids and risk of preeclampsia. Methods: Maternal intake of elaidic acid, one of the most abundant dietary trans fatty acids and other fatty acids were estimated using gas-liquid chromatography on erythrocytes from 22 women with preeclampsia and 40 normotensive controls. Fatty acids were expressed as the percentage of total fatty acids in erythrocytes. Logistic regression procedures were used to estimate odds ratios and 95% confidence intervals. Results: Mean levels of elaidic acid were 28% higher among preeclamptics (0.43 ± 0.12) as compared with controls (0.31 ± 0.12; p < 0.001). After adjusting for confounding factors, women with the highest levels of elaidic acid (median = 0.47) were 7.4 times (odds ratio = 7.4; 95% confidence interval 1.4–39.7) more likely to have had their pregnancy complicated by preeclampsia as compared with those women with the lowest levels (median 0.24). Risk of preeclampsia appeared to increase with increasing levels of elaidic acid (p value for linear trend = 0.05). Conclusion: These cross-sectional data suggest that diets high in elaidic acid may be associated with an increased risk of preeclampsia. This hypothesis should be examined in larger longitudinal studies.