An investigation was undertaken to determine the isolation rate and antibiotic resistance of Haemophilus influenzae from the nasopharynx of young children. The 996 subjects studied were up to 6 years of age. H. influenzae was isolated from 304 (30·5%) and strains of capsular type b from 11 (1·1%). Age, sibling status, season, respiratory infection and antibiotic therapy all influenced isolation rates. The overall prevalence of antibiotic resistance in the strains isolated was ampicillin 5·4% (all β-lactamase producers), cefaclor 0·3%, chloramphenicol 1·3%, erythromycin 38·2%, tetracycline 1·3%, trimethoprim 5·4% and sulphamethoxazole 0%. Ampicillin resistance was more common in type b than non-capsulated strains.