The aim of study was to evaluate the applicability of the PCR multiplex method for the identification of Streptococcus agalactiae (group B streptococci; GBS) serotypes and to indicate the participation of serotypes in the group of pregnant women. 1178 pregnant women at 35-37 weeks of pregnancy were studied between 2007-2009. Vaginal and rectal swabs collected from these women were tested for the presence of GBS. S. agalactiae identification was done basing on the culture method according to the CDC recommendations. For all isolated GBS strains the surface polysaccharides which conditioning serotypes were determined using commercially available serological latex kit and multiplex PCR method with two sets of specific primers. The frequency of GBS carriage among 1176 pregnant women was 30% (353 cases). Simultaneous colonization of the vagina and anus was demonstrated in 80% women, whereas GBS carriage only in the vagina or only in the anus was indicated in 9% and 11% cases, respectively. In pregnant women colonized by GBS serotype III (35%) dominated. The other serotypes were detected with the following frequency: Ia (20%), V (17%), II (15%), Ib (8%) and IV (5%). In the analyzed women population, GBS strains belonging to the VI, VII, VIII serotypes were not found. The results of our study show a great diagnostic usefulness of multiplex PCR method for identification of genes encoding GBS surface polysaccharides that are typical for individual serotypes.