Background In a case-control study of 100 preeclamptics and 100 controls, we assessed plasma transforming growth factor-β1 (TGF-β1) concentrations in relation to preeclampsia risk among Peruvian women with and without systemic inflammation. Methods Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Results The OR of preeclampsia increased across quartiles of TGF-β1 concentrations. Women with elevated TGF-β 1 and a proinflammatory profile experienced the highest risk of preeclampsia (OR = 15.4, 95% CI 4.7-50.4). Conclusions Our results confirm an association between TGF-β1 and risk of preeclampsia and extend the literature by indicating a strong association in women with systemic inflammation. © 2004 American Journal of Hypertension, Ltd.