Chlamydia trachomatis infection in the lower part of the genital tract of young girls and women may ascend to produce endometritis, salpingitis, perihepatitis, and other localized or generalized abdominal diseases. The resultant pain syndromes mimic a number of other common conditions that must be differentiated. A careful history and physical examination, with attention to historical and physical evidence of sexually transmitted disease, will alert the clinician to the possibility of chlamydial infection. Laboratory tests for C trachomatis may be helpful. However, tests of specimens from the lower genitourinary tract may yield negative results in patients with disease of the upper part of the genital tract and abdomen. Prompt recognition and treatment not only alleviate pain but also may help prevent inflammatory sequelae such as chronic painful adhesions, small-bowel obstruction, and tubal infertility. Costly workups and unnecessary surgery may also be avoided.