OBJECTIVE To assess whether C-reactive protein (CRP) concentrations in cervical amniotic fluid reflect the condition of the intrauterine environment in patients with preterm premature rupture of membranes (PROM) before 35 weeks of gestation. METHODS Amniotic fluid was obtained in 29 consecutive patients admitted with the diagnosis of preterm PROM earlier than 35 weeks of gestation either by amniocentesis or by collecting cervical fluid. CRP was measured in maternal blood, amniotic fluid, vaginal fluid and in cord blood obtained at delivery. Intraamniotic infection was defined as a positive amniotic fluid for aerobic or anaerobic bacteria, or Mycoplasma. The placentas and umbilical cords were examined for the presence of chorioamnionitis and funisitis. RESULTS A significant correlation was found between vaginal fluid CRP concentrations and both amniotic fluid (r = 0.95, p < 0.001) and umbilical cord levels (r = 0.47, p < 0.05). No correlation was found between maternal blood and vaginal fluid CRP concentrations. The proportion of patients with intraamniotic infection was 37.9% (11/29). The median (range) vaginal fluid CRP concentration was higher in patients with intraamniotic infection than in those with sterile amniotic fluid [901 (0-1354) vs. 507 (0-798) ng/mL, p < 0.001]. The median (range) vaginal fluid CRP concentration was higher in fetuses with (n = 12) than in those without funisitis (n = 17) [901 (598-1354) vs. 487 (0-1115) ng/mL, p < 0.01]. After adjustment for gestational age, vaginal fluid CRP concentration > 800 ng/mL remained a predictor of intraamniotic infection and funisitis. CONCLUSIONS Increased vaginal fluid CRP concentration is associated with intraamniotic infection and funisitis. As CRP is produced by hepatocytes and does not cross the placenta, its measurement in vaginal fluid might be an additional parameter for the assessment of fetal well-being in patients with premature PROM.