We sought to evaluate the administration of antibiotics to pregnant women with preterm rupture of membranes (PROM). We collected data by using the Cochrane Controlled Trials Register and MEDLINE. We included randomized controlled comparisons of antibiotic versus placebo (14 trials, 6,559 women). Antibiotics were associated with a statistically significant reduction in maternal infection and chorioamnionitis. There also was a reduction in the number of infants born within 48 hours and 7 days and with the following morbidities: neonatal infection (relative risk [RR] 0.67, 95% confidence interval [CI] 0.52-0.85), positive blood culture (RR 0.75, 95% CI 0.60-0.93), use of surfactant (RR 0.83 95% CI 0.72-0.96), oxygen therapy (RR 0.88, 95% CI 0.81-0.96), and abnormal cerebral ultrasound scan before discharge from hospital (RR 0.82, 95% CI 0.68-0.99). Perinatal mortality was not significantly reduced (RR 0.91, 95% CI 0.75-1.11). A benefit was present both in trials where penicillins and erythromycin were used. Amoxicillin/clavulanate was associated with a highly significant increase in the risk of necrotizing enterocolitis (RR 4.60, 95% CI 1.98-10.72). The administration of antibiotics after PROM is associated with a delay in delivery and a reduction in maternal and neonatal morbidity. These data support the routine use of antibiotics for women with PROM. Penicillins and erythromycin were associated with similar benefits, but erythromycin was used in larger trials and, thus, the results are more robust. Amoxicillin/clavulanate should be avoided in women at risk of preterm delivery because of the increased risk of neonatal necrotizing enterocolitis. Antibiotic administration after PROM is beneficial for both women and neonates.