1Ministry of Health, Muscat, Oman. Received: 15/09/02; accepted: 24/03/03 ABSTRACT A prospective cohort study was made of 386 first-grade primary-school children in Oman with active trachoma and 386 matched controls without trachoma. All children were educated about trachoma prevention. In addition, trachoma cases were treated with a single dose of oral azithromycin (20 mg/kg). Trachoma status was evaluated after 6 weeks, 6 months and 12 months. The follicles and inflammatory signs of active trachoma resolved 6 weeks or more after azithromycin treatment. The protection against subsequent trachoma infection cycles was optimal at 6 months (85.2% of cases, 99.0% of controls infection-free) but declined at 12 months (66.7% of cases, 98.2% of controls infection-free). Clinical evaluation seems to be a useful tool to evaluate the response of azithromycin to active trachoma cases in schoolchildren in a country with limited resources.