Trachoma is a blinding disease caused by ocular strains of Chlamydia trachomatis. The Carter Center and Proctor Foundation have been jointly conducting trachoma research in the Amhara region of Ethiopia for the past 10 years, through a series of clinical trials. We have found that repeated mass administration of oral azithromycin can greatly reduce the prevalence of trachoma, but mass antibiotics have been unable thus far to eliminate infection.