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 beta-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.