We conducted the study in Kahe Mpya subvillage, Rombo District, Tanzania. This community has been described previously. 15 (link) In July 2000, we examined each consenting resident for trachoma, using the simplified system of the World Health Organization. 16 (link) This grading system includes five signs: trachomatous inflammation–follicular, defined as five or more follicles at least 0.5 mm in diameter in the central plate; trachomatous inflammation–intense, defined as pronounced inflammatory thickening of the upper tarsal conjunctiva obscuring at least half the normal deep tarsal vessels; trachomatous scarring; trachomatous trichiasis; and corneal opacity. We then swabbed the tarsal conjunctiva of each subject’s right eye, using a highly standardized swabbing technique. 15 (link) Every nonpregnant resident 12 months of age or older was then offered one directly observed oral dose of 20 mg of azithromycin per kilogram of body weight (maximum, 1 g). Children younger than 12 months of age and pregnant women were not given azithromycin, but instead were offered two tubes of 1 percent tetracycline, with instructions to apply the ointment twice daily for 6 weeks. Azithromycin was donated by Pfizer through the International Trachoma Initiative, Dar es Salaam, Tanzania. Neither of these organizations had any role in the study design, data analysis, manuscript preparation, or the publication decision. Tetracycline was obtained on the open market. All treatment was provided free to subjects.