In July 1987 non-typable Haemophilus influenzae strains resistant to both ampicillin and chloramphenicol were isolated from the endotracheal aspirate of two children with pneumonia at Baragwanath Hospital, Johannesburg, South Africa. A study was therefore undertaken to determine the carriage rates of Haemophilus influenzae strains in the nasopharynx of children and staff in the index ward and in three control wards. Using a disc diffusion and an agar dilution method the susceptibility was determined of 100 isolates to ampicillin, chloramphenicol, erythromycin, rifampicin, amoxicillin/clavulanic acid, gentamicin, cefaclor, cefotaxime, tetracycline, sulphamethoxazole, trimethoprim and trimethoprim/sulphamethoxazole (1:19). The overall carriage rate of Haemophilus influenzae on admission was 76%. In the index ward, children carrying multiply resistant strains differed from the other children in that there was a longer mean duration of hospitalization, a lower proportion of males, and a higher proportion who had previously received antibiotics. All ampicillin resistant strains were shown to produce beta-lactamase. Only four isolates belonged to serotype b, of which three were ampicillin resistant and chloramphenicol sensitive while one was resistant to both drugs. Nasopharyngeal spread of resistant non-typable strains of Haemophilus influenzae was demonstrated to affect the management of paediatric patients in the hospital.