This study of lower genital tract infections in pregnant women attending antenatal clinics in Vientiane, Lao PDR is a response to the reported rapid increase in the number of HIV infections in neighboring countries, and is a recognition of the important role of reproductive tract infections in facilitating HIV transmission. This cross-sectional study determines the prevalence of lower genital tract infections among 500 antenatal attendees (gestational age < or = 20 weeks) attending two hospitals serving urban areas in Vientiane, between September 2001 and March 2002. Most participants were housewives (64.4%) and government workers (16.0%). Their husbands were mainly government officers (31.4%), laborers or farmers (30.2%), and businessmen (12.4%). Sixty-four percent reported a past history of "any vaginal complaints" with 44.2% having sought treatment. Candida spp had the highest prevalence of all infections (27.0%), followed by bacterial vaginosis (14.4% by Amsel's criteria and 22.0% by Nugent's score), C. trachomatis (10.2% by nucleic acid hybridization and 9.6% by PCR), T. vaginalis (1.8%), and N. gonorrhoeae (0.8%), but no syphilis serological markers. Taken in conjunction with other surveillance data from the same period, this study indicates an opportunity to prevent epidemic spread into the community of both sexually transmitted disease and HIV by appropriate preventative programed activities, including treatment services targeted at higher risk community groups.