A prospective multicentre study of Italian children with acute pharyngotonsillitis was carried out to determine the incidence of beta-haemolytic streptococcal infection and its epidemiological characteristics and to evaluate the effectiveness of a recently marketed macrolide, miocamycin. From February 1988 to March 1989, 865 children (aged 5 months to 14 years) were enrolled in 11 paediatric departments. Of these 31.9% had a positive throat culture for beta-haemolytic streptococci (26.6% group A streptococci, 5.3% group B, C, D or F). In 68.1% of the patients the throat culture did not yield any pathogen and the disease was considered to be probably viral. No epidemiological (age, season of occurrence, sex) or clinical characteristics (fever, pharyngeal hyperaemia, exudate etc.) could differentiate children with streptococcal pharyngotonsillitis from those with a probably viral one. Breese's score correctly identified only 19.1% of the cases with group A streptococcal infection. Miocamycin was given 50 mg/kg/day in 2 divided doses for 10 days in 225 children with streptococcal pharyngitis. The drug exhibited good clinical efficacy (resolution or improvement of acute signs and symptoms) in 96.3% of the children and a microbiological efficacy (eradication of the causative bacteria) in 85.3%.