Genital chlamydial infection is increasing and is now more common than gonorrhea. A sizable percentage of chlamydial infections of the lower genital tract in women progress to endometritis and salpingitis. Tubal infertility and ectopic pregnancy are important sequelae. Failure to control chlamydial infections reflects the following four factors: (1) Many cases are mild or asymptomatic; (2) diagnostic tests are expensive and technically demanding; (3) at least 7 days of multiple-dose therapy are currently required; and (4) partner notification is not routinely performed. Thus early identification of infected persons and compliance with curative therapy are less likely than with other sexually transmitted bacterial diseases.