Resistance of group B streptococcus (GBS) to antibiotics, particularly erythromycin and clindamycin, was studied. Erythromycin resistance was present in 22% of GBS isolates, and these isolates were constitutively resistant, inducibly resistant, or sensitive to clindamycin. Erythromycin and clindamycin MICs were related to the presence of ermA, ermB, or mefA genes.