Treatment programs for prevention of blindness from trachoma in areas of endemicity are based on mass therapy, i.e., the topical application of antibiotic to the eyes of all persons in affected communities. When oral antibiotics are administered as a supplement to topical therapy, the healing rates among children with severe-intensity trachoma significantly improve. Moreover, the use of oral antibiotics (either tetracycline or doxycycline) in selected cases is a cost-effective strategy, particularly in communities where less than 20% of children have active trachoma. Systemic antibiotic treatment should be given only to children with severe- or moderate-intensity disease--those at significant risk of developing blindness. Children should be monitored carefully during systemic chemotherapy for adverse reactions.