Pefloxacin mesylate is a broad spectrum fluoroquinolone active against pathogens with multiple resistance. Due to its high therapeutic efficacy (at last 90 per cent) and good tolerance pefloxacin mesylate is considered as the most promising drug in the therapy of severe infections and infections difficult for the treatment such as wound infection, meningitis and particularly perilous infections. Prolonged pharmacokinetics and high bioavailability of the drug provided its administration in the treatment of in- and outpatients with severe infection twice a day in a daily dose of 0.8 to 1.2 g. Pefloxacin proved to be a drug of choice in the treatment of infection due to intracellular pathogens.