Chlamydia trachomatis is the most common bacterial sexually transmitted disease in the United States and causes an estimated 4 million infections annually. Approximately 70% of infected women have few or no symptoms, and asymptomatic infection in women can persist for up to 15 months. Infection can progress to involve the upper reproductive tract and may result in serious complications. To identify women who may have chlamydial infections, CDC has recommended routine testing based on age, risk behavior, and clinical findings--especially in clinics and group practices that provide reproductive health care to adolescent and young women. This report describes the prevalence of chlamydial infections among patients visiting the family-planning clinic service of the San Diego County Department of Health Services from July 1989 through June 1993 and summarizes the findings of a survey in May 1993 that assessed chlamydia screening, reporting, and treatment practices for women who attended primary-care community-based clinics and group practices in San Diego County.