Background: Group B streptococcus (GBS) or Streptococcus agalactiae are members of the normal flora of the female genital tract. Maternal colonization has been found to be a major risk factor for invasive GBS disease within 6 days of birth. GBS has become the major cause of bacterial infections in the perinatal period, including bacteremia, amnionitis, endometritis, and urinary tract infection in pregnant women as well as sepsis and meningitis in neonates and young infants. Infection of the new born may be acquired by the intra-amniotic route or directly during passage through the birth canal. This study was undertaken to determine the prevalence of GBS colonization in pregnant women attending the antenatal clinic of Al-Hada Armed Forces Hospital in Western province, Taif, Saudi Arabia. This paper was the first data on incidence of GBS in pregnant women at Western province, Taif, Saudi Arabia. Methods: A total of 2,632 pregnant women were screened for GBS colonization between January and December 2014. Standard microbiological methods were used to isolate and identify GBS from vaginal and anorectal swabs obtained from study subjects. An antimicrobial susceptibility test was performed for all GBS isolates according to the criteria of the Clinical and Laboratory Standards Institute (CLSI) by disk diffusion method. Results: A total of 632 out of 2,632 (24%) pregnant women were colonized by GBS. Statistically significant association was observed for GBS colonization with any of socio-demographic characteristics of the study subjects including age, occupation, number of antenatal clinic visits, and type of gravida. All GBS strains were susceptible to penicillin, ampicillin, vancomycin and gentamicin, erythromycin, tetracycline, ceftriaxone, chloramphenicol, ciprofloxacin, clindamycin, and norfloxacin. Resistance was observed in some strains against clindamycin (0.18%). The data from the present study showed that incidence of GBS in Saudi pregnant women increased rapidly. These results are the first record of the database in Saudi Arabia at western province with high prevalence of GBS in pregnant women. Conclusion: This study showed that prevalence of GBS colonization was 24% among the study subjects. The finding of this study was comparable with findings reported from developed and developing countries. However, further epidemiological investigations should be done in different parts of the country (all provinces) in order to know the actual GBS colonization rate in pregnant women and to consider the use of intrapartum antibiotics prophylaxis for prevention of early onset GBS-neonatal diseases, considering the accelerated demand for reducing neonatal morbidity and mortality due to GBS. J Clin Gynecol Obstet. 2015;4(3):258-264 doi: http://dx.doi.org/10.14740/jcgo341w