New antimicrobial agents require careful assessment to determine whether they possess the appropriate properties for clinical use. Many new compounds of value in the prophylaxis and therapy of infections have been included in the current armamentarium. Close monitoring to identify possible adverse effects of new agents is essential. Alternative uses of older agents also expands therapeutic opportunities in the combat against infectious diseases. Inappropriate use of antimicrobial agents contributes to the worldwide problem of increasing bacterial resistance. The dramatic spread of such bacterial strains is partially responsible for the rising costs of infectious diseases. A rational and strict antibiotic policy is thus of great importance for the optimal use of these agents.