The purpose of this study was to determine whether there is a relationship between colonization of the genitourinary tract with group B Streptococcus (GBS) and prematurity. A search of the literature was conducted to identify articles addressing this issue. Ten studies provided enough data for a critical review; seven studies focused on genital colonization and three on asymptomatic bacteriuria. An association between cervicovaginal colonization with GBS and prematurity could not be demonstrated in six of the seven studies. However, women with asymptomatic bacteriuria caused by GBS had a higher rate of prematurity than did women without asymptomatic bacteriuria. We conclude that the weight of the available evidence does not support an association between prematurity and GBS colonization of the genital tract in the absence of asymptomatic bacteriuria.