We determined the predicting factors of early-onset group B streptococcal (EOGBS) infection in neonates who were born to GBS carrier mothers with inadequate intrapartum antibiotic prophylaxis (IAP). Medical records of all neonates born from January 1, 2008 to April 1, 2010 were reviewed. Inadequate IAP was defined as delivery less than 4 hours (h) after the first administration of antimicrobial. Of 1910 neonates, 273 were born from mothers colonized with GBS, including 69 who received inadequate IAP. Of 69 neonates, nine showed symptoms, including respiratory distress, fever, tachycardia, vomiting, and irritability. Abnormalities in complete blood count (CBC) and C-reactive protein (CRP) were noted in three and four neonates, respectively. Three infants were diagnosed with EOGBS infection confirmed by positive rectal and throat cultures, and all three presented with respiratory distress and CRP abnormalities. Respiratory distress (p=0.0004) and CRP (p=0.0001) offered reliable indicators for detecting EOGBS infections.