It is often proposed that the indiscriminate use of antimicrobial agents in the veterinary field leads to increased resistance in bacteria pathogenic to humans. Although for human medicine there is some potential danger behind the use of antimicrobial agents in animals, very few species (such as Staphylococci, Salmonella, Escherichia coli, Yersinia and Campylobacter) isolated in animals, which are also pathogenic to man, have been mentioned in the literature. The present paper analyzes the areas and bacteria where the clinician faces problems in the treatment of infection in man.