The purpose of this overview was to critically appraise all published randomized, controlled trials evaluating the efficacy of intrapartum chemoprophylaxis in reducing perinatal group B streptococcal infections. The Oxford Database of Perinatal Trials, Medline, Excerpta Medica, and personal files were used for the literature search. By means of present inclusion criteria to select relevant articles, two independent researchers identified nine randomized, controlled trials. Three trials were excluded because of duplicate publication, one because the randomization process was violated, and one because the outcome data were collected retrospectively. The quality of the methods of the four accepted trials was poor, and because of basic flaws meta-analyses of trial results were not performed. Results of three studies showed a statistically significant reduction in neonatal group B streptococcal colonization rates with intrapartum chemoprophylaxis. Although a trend toward a reduction in proved neonatal infection was reported in three studies, each lacked the power to reach statistical significance. Intrapartum chemoprophylaxis to reduce perinatal group B streptococcal infections is not supported by conclusive evidence from well designed and conducted randomized, controlled trials.