PIP: A survey was conducted in 1981 to identify risk factors associated with chlamydial infection and to evaluate the efficacy of presumptive therapy. Chlamydia trachomatis was recovered from the cervices of 9.8% (268/2729) of women attending 7 family planning clinics in San Francisco; the infection rate varied from 5.5-22.5% in different clinics. The highest recovery rate was in an inner city clinic (22.5%), lowest rates (5-6%) in the 2 clinics whose clientele tended to be middle class. The most easily identifiable risk factor is the age of the population: 16% of women between ages 15-19 were infected, 10.8% of those 20-24, 6% of the 25-29 age group, and less than 2.5% of those over age 30. Infected women were also more likely to be nulliparous, never married, oral contraceptive users, black, and living in poverty areas. For women with signs of urinary tract infections, negative bacterial cultures, or mucopurulent endocervicitis 35.8% were infected as compared to 8.3% of women who lacked these signs. Tetracycline was used to treat uncomplicated chlamydial infection (1 g/day for 14 days). These predictors have proven to be effective in venereal disease clinic populations and the 4 presumptive indicators for treatment (partner with nongonococcal urethritis, confirmed gonorrhea, sterile pyuria, or mucopurulent endocervicitis) were only marginally useful for women attending family planning clinics for routine visits. Unfortunately laboratory procedures are still expensive and a cheaper method of diagnosis is needed. It is recommended that whenever patients are being treated for any condition for which the choice of drugs includes one effective against chlamydia trachomatis, that drug should be chosen over others.