Two hundred strains of Streptococcus pyogenes were isolated at random from septic lesions not associated with the respiratory tract and nose and throat in 19 centers throughout Poland and typ-ed by T-agglutination. The prevalent types of S. pyogenes were: 8, 25, Imp. 19 complex in 29% (with occurrence of the 25, Imp. 19 type in 14%, 3, 13, B 3264 complex in 24.5% (type 3 only in 12%), 5, 11, 12, 27, 44 complex in 24 % (type 12 only in 7.5 %), and type 4 in 10.5 %. Other types constituted 11.5 %. These strains were tested for their susceptibility towards 30 antibiotics, of which the most effective occurred: natural and semisynthetic penicillins, cepha-lotin, rifamycins, erythromycin, spiramycin, pristinamycin and lincomycin. Twenty-two per cent of strains were tetracycline-resistant, 13.5 % – chloramphenicol-resistant and 30.5 % – novobiocin-resistant. All strains were not susceptible to streptomycin and the neomycin group of antibiotics at concentrations available in the organism. Distribution of serotypes among antibiotic-resistant strains is described. Prevalence of serotypes of S. pyogenes recognized in this study was compared with occurrence of serotypes in 2451 strains of S. pyogenes isolated from non-epidemic and epidemic-infections caused by this microorganism during the 1950–1965 period.