Trachoma is in a sense two diseases: the infection most apparent in children and the blinding sequelae found in adults. Ocular strains of Chlamydia trachomatis cause repeated episodes of conjunctivitis, with the peak prevalence of infection usually occurring in 3–5 year olds.¹ Progressive scarring, entropion, and trichiasis lead to blinding corneal ulceration, typically some 40 years or more later.² This long lag time between infection and blindness has always been somewhat of a puzzle. Several explanations have been offered. The normal, age related decrease in tears, goblet cells, and lid elasticity may make the elderly more prone to the effects of scarring.³ Existing scars may contract slowly over time. Further episodes of chlamydial infection may cause scarring to progress.^4,5 If this last hypothesis is the case, then the frequent recurrence of trichiasis after surgical repair could in part be because of recurrent infection. This is a testable hypothesis. A single dose of oral azithromycin is effective in eliminating chlamydial infection …