Streptococcus pneumoniae is frequently carried in the nasopharyngeal flora and remains a leading cause of bacterial infection in young children. The same serogroups (6, 14, 19, 23) are frequent in the carriage, the most common cause of otitis media and systemic infection before 3 years of age, and implicated in the antibiotic resistance. The increasing number of S. pneumoniae resistant to penicillin and other antibiotics deserves to set up an epidemiologic survey. Between november 1990 and march 1994, 1476 nasopharyngeal bacteriological samples were performed by our group of pediatricians and ENT specialists in Paris area. There has been an alarming increase in antibiotics resistance: in 1994, 43% of S. pneumoniae strains showed a diminished susceptibility to β-lactam antibiotics. Young children attending in day care center harbour more frequently S. pneumoniae. Children with rhinopharyngitis or acute otitis media (particularly those with high fever and otalgia) are more frequently colonized by this bacteria species than controls.