The aims of this study were to estimate pneumococcal carriage rate, antimicrobial resistance and serogroup distribution of nasopharyngeal isolates of Streptococcus pneumoniae among children with acute upper respiratory infections (AURIs) aged 1 month to 5 years attending outpatient department of the Beijing Children's Hospital between 2000 and 2005. Susceptibilities to penicillin, amoxicillin-clavulanic acid, ceftriaxone, cefuroxime, cefaclor, erythromycin, tetracycline, sulfamethoxazole-trimethoprim and chloramphenicol were assessed using the E-test and disc diffusion. We also analyzed the correlation between antibiotic consumption and rates of resistance. The prevalence of penicillin-nonsusceptible pneumococci increased from 26% during 2000-2001 and 21% during 2002-2003 to 31.5% in 2004-2005. The percentage of S. pneumoniae resistant to cefaclor and cefuroxime increased from about 6% during 2000-2001 to about 23% during 2004-2005 (P < 0.01). The frequency of resistance to erythromycin ranged from 87% to 94%. Tetracycline and co-trimoxazole resistance rates were greater than 80%. We conclude that resistance rates for most antibiotics are increasing, possibly due to misues of antibiotics in the hospital setting. However, chloramphenicol resistance was found to decrease, which correlated with the cessation of chloramphenicol administration in 1999. Pneumococcal strains (n=519) were analyzed by serogroup, and only 296 were found to be seven-valent pneumococcal conjugate vaccine-related serotype isolates. This serotype distribution is important for surveillance of the new conjugate vaccine.