A 23-year-old woman had endometritis due to Chlamydia trachomatis infection. Chlamydia trachomatis was cultured from endometrial tissue obtained by biopsy, and elevated levels of serum antibodies, including IgM antibodies, to C. trachomatis were found. Cervical secretions were also positive for antibody. After treatment with tetracycline, endometrial cultures for C. trachomatis were negative and endometrial inflammation disappeared. Chlamydia trachomatis has been implicated in salpingitis, cervicitis, urethritis, and peritonitis, This case shows that endometritis may also result from C. trachomatis infection and in such instances may be a contributing factor in infertility.