Hypertension is the most frequent medical complication of pregnancy. A recent report demonstrates the flogistic pathogenesis of pregnancy-induced hypertension. Because C-reactive protein (CRP) is a marker of inflammation, it can be used in the differential diagnosis of hypertensive disorders of pregnancy. A total of 322 pregnant women at 24 to 32 weeks' gestation were enrolled. The control group (A) comprised 190 women. Sixty-three women had preeclampsia (PE, group B), 31 women presented transient hypertension (TH, group C), 19 had HELLP syndrome (HS, group D) and 19 had chronic hypertension (CH, group E). CRP serum concentrations were significantly higher in groups B, C, and D in comparison with the group A. In the whole population, systolic and diastolic pressure value inversely correlate with weight at delivery and weeks of gestation at delivery. CPR levels in patients with PE and HS inversely correlate with birth weight and gestational week at delivery. Normal plasma levels of CRP may be an important marker of differential diagnosis between TH and CH. In TH, PE, and HS, CRP levels were higher than in the control and CH groups, suggesting that inflammation may be the common pathogenetic cause of TH and PE. Finally CRP levels in preeclampsia are believed to correlate with preeclamptic process severity.