Aim: The expressions of caveolin-1 have only been examined in the placental tissue of patients with preeclampsia and were reported to be low. Therefore, we decided to investigate the maternal serum levels of caveolin-1 in patients with preeclampsia. Material and methods: This cross-sectional study was conducted including 87 pregnant women; 32 with normal pregnancy and 55 with preeclampsia. Maternal serum levels of caveolin-1 were measured by using enzyme-linked immunosorbent assay kit (ELISA). Results: The mean serum caveolin-1 level was significantly lower in women with preeclampsia (PE) compared with the control group (11.48 +/- 0.92 versus 12.94 +/- 1.36 ng/ml) and being lowest in the early onset PE group (11.24 +/- 0.74 ng/ml). Serum caveolin-1 concentrations did not correlate with maternal age and BMI. However, caveolin-1 concentrations were negatively correlated with systolic blood pressure (r = -0.467, p = .001) and diastolic blood pressure (r = -0.441, p = .001) as well as with umbilical artery resistance index (r = -0.275, p = .01). Conclusion: Maternal serum caveolin-1 levels are significantly lower in patients with PE than controls. The serum caveolin-1 levels inversely correlate with blood pressure and umbilical artery Doppler parameters.