In an open study, 70 in-patients and 23 out-patients aged between 1 and 14 years with sinusitis (n = 1), perforated otitis media (n = 4), pharyngotonsillitis (n = 25), tracheobronchitis (n = 30) or broncho-pneumonia (n = 33) were treated daily with a combination of 40 mg/kg amoxycillin and 10 mg/kg clavulanic acid in three equal doses for between 6 and 15 days. Purulent specimens were cultured when obtainable and pathogenic organisms identified were Staphylococcus aureus, beta-haemolytic streptococcal group A, Pseudomonas aeruginosa, Pseudococcus species and Klebsiella pneumoniae infections, of which 45.7% were beta-lactamase-producing and 54.3% were ampicillin-susceptible. After treatment, only one beta-lactamase-producing Streptococcus and one Staphylococcus infection persisted. Side-effects (vomiting, nausea, diarrhoea, maculopapular exanthema, rash) occurred in 16 patients and treatment was withdrawn in eight. It is concluded that the amoxycillin--clavulanic acid combination is a suitable first choice for the treatment of respiratory tract infections in children in whom the pathogenic organism may not have been established.