The autors pointed out that contamination may be exogenous, as a result of invasive diagnostic techniques, patient preparation, surgery, catheter insertion and wound dressing, or endogenous, especially in patients with specific risk factors (age, metabolic disorder, malnutrition, immunodeficiency) and aspecific risk factors (anesthesia, blood transfusion, surgery). Pharmacologic prophylaxis of infection may be unspecific (artificial nutrients, anticoagulants, immunomodulators) or specific (antibiotics). Prophylaxis is indicated in clean-contaminated and contaminated surgery; antibiotic chemoprophylaxis is also indicated in risk patients and permanent prosthesis surgery. The authors emphasized that antibiotics are no substitution for careful surgery.