To obtain information on the Streptococcus pneumoniae carrier state in Spanish children, 332 healthy 6-year-old children from nine primary schools in northern Spain were screened. Thirty-six percent of the children had positive cultures yielding 128 strains. Seventy-one strains belonged to 14 serogroup/serotypes, the most frequent being 19, 23, 3, 24 and 11. Fifty-seven strains were nontypeable. The identification of strains with equivocal results was confirmed at species level by means of hybridisation with a specific probe, pneumolysin-mediated agglutination and a pathogenicity test in mice. Sixty-four percent of strains showed resistance to penicillin, 22% of these also being resistant to cefotaxime. More than 40% of the strains were resistant to trimethoprim-sulfamethoxazole, tetracycline and erythromycin. Twenty percent of the erythromycin-resistant strains were susceptible to clindamycin. Two strains were resistant to rifampicin and one strain was resistant to ofloxacin. All strains were susceptible to vancomycin. Previous antibiotic administration and having siblings under the age of 2 years correlated with the carriage of pneumococcus. There was no correlation with the carriage of antibiotic-resistant strains, or a record of previous infections, previous hospital admissions or having relatives with chronic respiratory disease.