To compare the diagnostic value of soluble intercellular adhesion molecule 1 (sICAM-1) with that of c-reactive protein (CRP) for detecting chorioamnionitis (CAM) in serum of women with premature rupture of membranes (PROM), 55 pregnant women with PROM, including 18 pregnant women with preterm premature rupture of membranes (PPROM) and 20 normal pregnant women at term (TPROM) were studied. Maternal serum were measured by Sandwish enzyme-linked immunoabsorbent assay (ELISA) for sICAM. CAM was histologically confirmed after delivery. The results revealed that (1) maternal serum levels of sICAM-1 and CRP were significantly higher in women with PROM than those without it; (2) maternal serum levels of sICAM-1 and CRP were significantly higher in women with CAM than those without it; (3) serum levels of sICAM-1 in PPROM women were similar to those in TPROM women, whereas serum levels of CRP in PPROM women were significantly higher than those in TPROM women; (4) the sensitivity, specificity, positive predictive value, negative predictive value, Kappa index and area under receiver operating characteristic (ROC) curve of maternal serum sICAM-1 (cutoff 104.7 ng/ml) and CRP (cutoff 1.03 mg/dl) for diagnosing CAM were 100%, 91.2%, 87.5%, 100%, 0.20, 0.995 and 81.0%, 73.5%, 65.4%, 86.2%, 0.13, 0.811, respectively; (5) among the mild histological CAM group, severe histological CAM group and clinical CAM group, the difference in maternal serum levels of sICAM-1 were significantly (P<0.001), with the order of concentration from high level to low level corresponding to the severity of CAM. It is concluded that maternal serum level of ICAM-1 is superior to that of CRP as biomarker for diagnosing intraamniotic infection in pregnant women with PROM.