Periventricular leukomalacia, a common brain white matter lesion in preterm neonates, is a major risk factor for cerebral palsy. Recently, cytokines (i.e., tumor necrosis factor and interleukin-1(beta)) have been implicated as mediators for the development of periventricular leukomalacia. The purpose of this study was to examine the relationship between umbilical cord plasma levels of tumor necrosis factor-alpha, interleukin-1(beta), interleukin-6, and interleukin-1 receptor antagonist and the occurrence of periventricular leukomalacia in preterm neonates. Umbilical cord blood was collected from 172 consecutive preterm births (25 to 36 weeks). Periventricular leukomalacia-associated lesions were diagnosed by brain ultrasonography within the first 3 days of life. Tumor necrosis factor-alpha, interleukin-1(beta) interleukin-6, and interleukin-1 receptor antagonist were measured by sensitive and specific enzyme-linked immunoassay methods. Umbilical cord arterial pH was measured at birth. Statistical analysis was performed with multiple logistic regression and receiver operating characteristic curve analysis. Periventricular leukomalacia-associated lesions were present in 14.5% (25/172) of infants. Plasma concentrations of interleukin-6 but not of tumor necrosis factor-alpha, interleukin-1(beta), and interleukin-1 receptor antagonist were significantly higher in neonates with periventricular leukomalacia-associated lesions than in those without these lesions (median 718, range or = 400 pg/ml had a sensitivity of 72% (18/25) and a specificity of 74% (108/147) in the identification of periventricular leukomalacia-associated lesions. Multivariate analysis showed that umbilical cord interleukin-6 was an independent risk factor for periventricular leukomalacia (odds ratio 6.2, p < 0.002) after correction for known confounding variables (i.e., gestational age at birth, umbilical artery pH, chorioamnionitis). Interleukin-6 concentrations in umbilical cord plasma are elevated in neonates with periventricular leukomalacia-associated lesions. Our data support the hypothesis that periventricular leukomalacia may be the result of cytokine-mediated brain injury.