Brain injury is common in very preterm infants, and intrauterine infection is a frequent antecedent of preterm birth. We examined the relation of cerebral damage to intrauterine antigen exposure and inflammation in 50 infants who were born at 23-29 weeks' gestation. Higher concentrations of cytokines (tumour necrosis factor alpha [TNF-alpha], and interleukins [IL], 1beta, 6, and 10) and CD45RO(+) T lymphocytes in umbilical blood predicted cerebral lesions detected by magnetic resonance imaging very soon after delivery. Our results suggest that infants who mount an immune response in utero are at higher risk of cerebral lesions.