1 2 Peter Reeve and Lavelle Hanna lSmith Kline & French Laboratories, Research and Development, 709 Swedeland Road, Swedeland, PA 19479, USA 2Department of Microbiology, S-412, University of California, San Francisco, San Francisco, CA 94143, USA Trachoma, an infectious keratoconjunctivitis due to chlamydial infection, was one of the earliest recognized clinical entities. References to it have been noted in Egyp tian papyri and in Greco-Roman medical treatises. Since those times it has remained a most important eye infection, and indeed trachoma is still a major cause of blindness in rural...