Antibiotic sensitivities of peptostreptococci, streptococci, Actinomyces, bacteroid, and fusobacterial strains pathogenic for the periodontium are analyzed. The sensitivities of these bacteria to broad-spectrum penicillins, cephalosporines, lincomycin, and macrolides, and to metronidasole and nitasole are assessed. New macrolide drugs macropen and rulide and gramicidine C, levomycetine, and rifampicin are highly active towards the above microflora. Microbiological indications for oral and local use of these antibiotics are validated. Some narrow-spectrum antibiotics, such as augmentine, cephalexin, and vancomicin are highly active, too; the latter drug is specifically active towards Actinomyces.