Group B streptococcus (GBS) neonatal sepsis is a serious disease causing newborn mortality and long‐term neurologic sequelae. The Centers for Disease Control and Prevention (CDC) recommend third‐trimester GBS screening and intrapartum antibiotic prophylaxis for high‐risk women. The aim of our study was to identify colonized pregnant women and assess the prevalence of GBS in pregnancy and the susceptibility pattern of GBS in southern Taiwan. We performed the study at the Department of Obstetrics and Gynecology, Kaohsiung Women and Children' Hospital, between January and December 2002. Distal vaginal and anorectal swabs were obtained from pregnant women at 35 or more weeks' gestation. Swabs were used to inoculate selected medium, which was subcultured onto sheep' blood agar after 24 hours. Sensitivity to azithromycin, clindamycin, erythromycin, ofloxacin, penicillin G, tetracycline, trimethoprim/sulfamethoxazole, and vancomycin was tested using the disc diffusion method. Of the 374 pregnant women enrolled in the study, 56 (15%) had positive cultures for GBS. Antibiotic susceptibility was as follows: azithromycin 44.6%, clindamycin 66.1%, erythromycin 70.5%, ofloxacin 70.5%, penicillin G 60.7%, tetracycline 39.3%, trimethoprim/sulfamethoxazole 35.7%, and vancomycin 100%. The CDC recommend penicillin as the first choice for intrapartum prophylaxis, with erythromycin and clindamycin as alternatives for penicillin‐allergic patients. There has been increasing resistance to these antibiotics among GBS. Third‐trimester GBS screening and susceptibility testing for pregnant women should be considered.