Repeat infections with Chlamydia trachomatis are associated with increased risk for long-term sequelae. The authors analyzed the frequency and predictors of repeat chlamydial infection by using a population-based chlamydia registry in Washington State and evaluated whether women would seek care at the same clinic for repeat infections. Among 32,698 women with an appropriately treated initial chlamydial infection during 1993-1998, 15% developed one or more repeat infections during a mean follow-up time of 3.4 years. Among women less than age 20 years at the time of initial infection, 6% were reinfected by 6 months, 11% by 1 year, and 17% by 2 years. Young age was the strongest predictor for one and two or more repeat infections after controlling for the length of follow-up and other variables. Only 36% of the repeat infections were diagnosed at the same clinical setting as the initial infection, and 50% were diagnosed at the same type of clinic. Adolescent girls had the least consistency in the source of care for chlamydia. This study suggests that efforts to prevent repeat chlamydial infection in young women remain an urgent public health priority and that the burden of repeat infection may be substantially higher than estimates from clinic-based studies.