OBJECTIVES: To determine whether women who collect self-collected vaginal swabs at home demonstrated a higher positivity of Chlamydia trachomatis than women in family planning clinics. METHODS: Collection kits for vaginal swabs were internet requested, collected at home, and mailed to a laboratory for testing; questionnaires were completed about acceptability and sexual risk history. Infected women received treatment at participating clinics. Age-specific prevalences were compared to those from family planning clinics. RESULTS: Chlamydia positivity was 10.3% for 1171 females mailing swabs; prevalences ranged from 3.3% to 5.5% in family planning. Positivity for internet age groups was much higher than those for family planning age groups. The positivity for internet participants ranged from a low of 4.4% in Baltimore in 2005 to a high of 15.2% Baltimore in 2007. Family planning clinic prevalence in Baltimore and Maryland ranged from a low of 3.3% in Baltimore in 2006 to a high of 5.5% in Baltimore in 2008. The median age for all years for internet users in Baltimore and Maryland combined was 23 years; the median age for all years for attendees to family planning clinics who had chlamydia testing performed was 23 years. CONCLUSIONS: Internet recruited women demonstrated higher positivity of chlamydia than those in family planning, providing new options for chlamydia screening programs.