Infection with Chlamydia trachomatis can be either symptomatic or asymptomatic. In adults, complications include infertility, chronic pelvic pain and ectopic pregnancy. Complications in newborns include conjunctivitis and pneumonia. Screening of asymptomatic women at high risk for the disease can identify candidates for antibiotic therapy. Until recently, chlamydia cell culture was the only diagnostic test and it was not widely available. Because the specificity of cell culture is 100 percent, it remains the standard against which other tests are measured. The recent development of nonculture tests makes it feasible for most laboratories and physicians' offices to offer testing. The main disadvantage of nonculture tests is low specificity. A positive screening test in a woman at low risk should be confirmed by a second test. Routine screening and treatment of patients who are at high risk can decrease the incidence, complications and transmission of chlamydial infection.