With use of standardized techniques, a study of nasopharyngeal pneumococcal carriage in children in six Central and Eastern European cities was undertaken during the winter of 1993-1994. Nasopharyngeal swab specimens were collected from 954 children (predominantly under the age of 5 years) who were hospitalized or attending outpatient clinics or day-care centers. Susceptibility of isolates was determined by disk diffusion (on Mueller-Hinton agar with 5% sheep blood). Disks containing 1 micrograms of oxacillin were used to screen for susceptibility to penicillin G. Pneumococci were recovered from 258 (27.0%) of the 954 children. A variety of strains were recovered, and most penicillin-resistant strains were ŕesistant to multiple agents. Minimum inhibitory concentrations of penicillin for selected resistant strains were 0.125-8 micrograms/mL. Resistance to penicillin was common in strains from Bulgaria, Romania, and Slovakia. Resistance to erythromycin and chloramphenicol occurred in Bulgarian and Romanian strains. Strains from Poland were all susceptible to penicillin, but many were resistant to tetracycline. Resistance to trimethoprim-sulfamethoxazole was common in Bulgarian, Romanian, and Slovak strains. Czech and Russian strains were predominantly susceptible to antibiotics. Most resistant strains were of serotypes 6, 14, 19, and 23.