An earlier study at Group Health Cooperative of 1692 largely asymptomatic young women attending primary care clinics found a prevalence of chlamydial infection of 3.5 percent.17 An age of less than 25 years, black race, nulligravidity, two or more sexual partners in the past year, douching within the past year, the presence of cervical ectopy, and being unmarried were independently associated with an increasedrisk of chlamydial infection.