The bacterial flora of the nose and nasopharynx was studied in 86 healthy young men. Common pathogens (Haemophilus influenzae and Streptococcus pneumoniae) were isolated from only 6 % of all 172 nasal cavities. The same pathogens were isolated from 27 % of 86 nasopharyngeal samples. H. influenzae dominated over S. pneumoniae both in the nose and the nasopharynx. No culture either from the nose or nasopharynx grew Streptococcus pyogenes. Potentially pathogenic bacteria, non-group-A hemolytic streptococci and various groups of Neisseria meningitidis were isolated from the nasopharynx in 20 % of the subjects. According to the present study healthy adults do not carry group-A hemolytic streptococci in the nose and seldom if ever in the pharynx. Thus, isolation of S. pyogenes by bacterial culture is suggestive of a bacterial infection by this agent at these sites. Isolation of hemolytic streptococci other than group A from the pharynx does not necessarily indicate bacterial infection, and the same holds true for H. influenzae and S. pneumoniae.