A total of 389 children (age 0-6-102 years) with typical signs and symptoms of acute otitis media were randomized (1:1) to treatment with either azithromycin or coamoxiclav. The dosage schedule for azithromycin was 10 mg/kg/day, in a single daily dose, administered for three days. Co-amoxiclav was given at a dose of 13-3 mg/kg (amoxycillin equivalent) tid for ten days. Patients were evaluated 4-6 days and 12-16 days after the start of therapy. A satisfactory clinical response was reported for 93-2% of the 192 evaluable azithromycin-treated patients (144 cured, 35 improved), and for 97-3% of the 189 evaluable co-amoxiclav-treated patients (148 cured, 36 improved). Six (3-0%) relapses occurred in the azithromycin group, and four (21%) in the co-amoxiclav treatment group, respectively. Side-effects were recorded in a significantly fewer number of the azithromycin patients (23 of 197; 11 -7%) compared with the co-amoxiclav patients (43 of 192; 22-4%, P < 0-02). Adverse events were mainly gastrointestinal in nature, with diarrhoea the most frequent complaint (32 cases with co-amoxiclav; five with azithromycin; P < 0-001). One patient from each group discontinued therapy because of treatment-related adverse events. Laboratory analyses (mainly haematologjcal in nature) showed abnormalities in six of 100 azithromycin patients and ten of 101 co-amoxiclav patients. It was concluded that three-day, single-dose azithromycin and ten-day tid co-amoxiclav therapy have comparable clinical efficacy in paediatric patients with acute otitis media; however, there was a lower incidence of side effects in the azithromycin group.