BACKGROUND: Black race is a risk marker for Chlamydia trachomatis infection. Because chlamydial serovar and race could both influence the transmission dynamics of chlamydia, studies characterizing serovars in a predominantly black population are of interest, yet remain sparse. STUDY DESIGN AND GOALS: C. trachomatis isolates collected consecutively from 109 female and 98 male patients presenting to a sexually transmitted disease clinic in Birmingham, Alabama, were serotyped. Our goal was to evaluate serovar distribution and associated demographic characteristics in a predominantly black population. RESULTS: The median age was 23 years and 91% were black. Serovars E (29%), D (19%), F (19%), Ia (16%), and J (9%) were the most prevalent. Blacks were less often infected with serovar E (30% vs. 41%) and J (9% vs. 24%), but more often infected with serovar Ia (17% vs. 0%) compared with individuals of other racial groups (P = 0.07). The overall serovar distribution did not significantly differ by gender or age; however, serovar Ia infections were associated with older age (21% in age ≥23 years vs. 10% in those age <23 years; P = 0.03). CONCLUSIONS: Although the overall C. trachomatis serovar distribution in this predominantly black population in Birmingham was similar to that reported elsewhere, serovar Ia was only found in blacks, in whom it was commonly isolated. Finding differences in serovar distribution by race, particularly serovar Ia, may be of epidemiologic significance and deserves verification in similar cohorts. Copyright © 2006, American Sexually Transmitted Diseases Association All rights reserved.