Guidelines recommend intrapartum antibiotic prophylaxis (IAP) for parturient women who have a screen positive for group B Streptococcus (GBS). Clindamycin should be used for IAP only if the maternal GBS isolate is susceptible. We report a case of clindamycin-resistant GBS disease in a newborn infant whose mother received clindamycin IAP, and we review clindamycin susceptibility testing.