Three hundred and two samples of biological material from patients operated because of acute inflammatory states of abdominal cavity were investigated. Both aerobic and anaerobic bacteria were investigated. Among aerobic flora most frequently occurred enterococci, E. coli and Pseudomonas. Bacteroides and Peptostreptococcus were most frequently occurring anaerobes. Mixed flora was seen very often. Isolated microorganisms were tested for susceptibility to ciprofloxacin, cefoperazone, cefotaxime, gentamicin, netilmicin and in cases of anaerobes to metronidazole.