Antibiotic sensitivity of 466 clinical strains of gram-positive and gram-negative microorganisms isolated from patients with different forms of pyoinflammatory diseases was studied. Most of the staphylococcal isolates were resistant to benzylpenicillin (74.3 per cent). The number of the isolates resistant to erythromycin amounted to 59.6 per cent. The respective figures for methicillin and dicloxacillin were 17.9 and 10.8 per cent. Staphylococci resistant to new aminoglycosides, fusidin and rifampicin were rare. It was shown that. P. aeruginosa preserved its sensitivity to the majority of the antipseudomonas antibiotics. Among Enterobacteriaceae the highest levels of antibiotic resistance were observed in Enterobacter, Citrobacter, Serratia and Klebsiella. Significant variation in the isolation frequency of different microbial species and in the proportion of gram-negative and gram-positive bacteria in the hospital departments was observed. It was noted that gram-negative causative agents predominated in the departments of chest and abdominal surgery, anesthesiology, intensive care and urology.