Resistance to commonly used antimicrobial agents among the key respiratory pathogens is increasing worldwide and therefore a rational choice of an empirical treatment requires knowledge of both global and local resistance patterns. The susceptibility of 185 Streptococcus pneumoniae and 169 Haemophilus influenzae isolates collected from January 1999 to May 2002 at the Children's Memorial Health Institute, Warsaw, Poland, from 351 children with community-acquired respiratory tract infections (RTIs) has been determined. Of S. pneumoniae isolates, 84% were susceptible to penicillin, 91% to cefaclor, 95% to cefuroxime, 98% to cefotaxime, 79% to erythromycin, 46% to co-trimoxazole, 82% to clindamycin and 59% to tetracycline. The majority (83%) of erythromycin-resistant isolates tested carried the erm(B) gene, conferring the MLS(B) phenotype. All tetracycline-resistant S. pneumoniae strains analysed were tet(M) positive and tet(O) negative. A total of 24% of H. influenzae isolates were beta-lactamase-positive. H. influenzae susceptibility to amoxicillin/clavulanate, cefaclor, cefuroxime, azithromycin, tetracycline and co-trimoxazole was 100, 89, 94, 96, 96 and 43%, respectively.