Group B Streptococcus (GBS) is an important infectious organism in pregnant women and their neonates. Although excellent data are available from the developing world, little epidemiologic information is available from Latin America. To evaluate the prevalence of GBS colonization in a developing country, a prospective study was performed in Lima, Peru. We found a relatively low prevalence of GBS colonization of 6.0% in parturient women and 10.6% in nonpregnant women. No association of GBS colonization was made with previously identified risk factors such as age, parity, or birth control practices. We did find a positive association between GBS colonization and chlamydial carriage (P < 0.05). We also report an even distribution of GBS serotypes: Ia/c = 35%, IIc = 18%, III = 29%, and V = 18%. Our study provides evidence for a low prevalence of GBS maternal carriage in this urban Latin American population.