Abstract Objective To examine the relationship between amniotic fluid (AF) white blood cell (WBC) count and the presence and severity of inflammatory lesions of the placenta in women with preterm premature rupture of membranes (PPROM). Methods This retrospective cohort study included 90 consecutive women with PPROM (24.0-35.6 weeks) who met the following criteria: singleton gestation; transabdominal amniocentesis performed to obtain AF for culture and WBC count; delivery within 72 hours of amniocentesis; placental histologic examination after preterm delivery. Results The prevalence of histologic chorioamnionitis was 32% (29/90) and that of positive amniotic fluid culture was 21% (19/90). Patients with histologic chorioamnionitis had a significantly higher AF WBC count than those without this lesion. Logistic regression analysis demonstrated that AF WBC count had a significant relationship with histologic chorioamnionitis after controlling for gestational age and AF culture. The median AF WBC count increased significantly according to the higher severity of inflammation in each type of placental histologic section. According to receiver operating characteristic curve analysis, the best cutoff value of AF WBC count for predicting histological chorioamnionitis was 25 cells/mm 3 , with a sensitivity of 62% and a specificity of 77%. Conclusion Both the presence and greater severity of inflammatory lesions of the placenta are associated with an elevated AF WBC count. AF WBC count is an important and independent predictor for inflammatory lesions of the placenta in women with PPROM.