Pneumococcus is one of the most common bacterial pathogens in children with upper respiratory tract and invasive infections. Its main reservoir is the human nasopharynx. Nasopharyngeal colonization of S. pneumoniae is more common in young children attending day-care centres. At least 90 serotypes have been recognised, although only a fraction of these serotypes are implicated in invasive disease. Pneumococcal resistance to penicillin and other antibiotics has emerged rapidly in recent years. Antibiotic use at both the community and individual levels have been identified as the strongest risk factor for the carriage and spread of resistant pneumococci. The genetic basis of resistance in S. pneumoniae is associated with different clinically relevant mechanisms. The clinical impact of pneumococcal resistance varies with the site of infection and is better documented for meningitis and otitis media than for pneumonia. A heptavalent pneumococcal conjugate vaccine has been shown to be highly effective in preventing invasive disease in children under 2 years of age.