A longitudinal study of the nasal carriage of coagulase-positive staphylococci among 373 children from a rural county revealed that 118 (32%) children never harbored such organisms over an 8-mo period. Sixty-four (17%) of the children were found to be persistent carriers. There was no measurable dissemination of staphylococci from the hospital to the community group under study. Staphylococci of phage type 80/81 were found to constitute only 6% of all strains isolated. Sharp increases in the incidence of penicillin-resistant strains were encountered after the administration of antibiotics to these children. The acquisition rate of new strains increased from 6.7% to 13.3% after antibiotic therapy. Carriers of penicillin-sensitive strains were seen most frequently to acquire new sensitive strains, whereas carriers of resistant strains most frequently acquired new resistant strains.