The term antimicrobial can be applied to any compound that inhibits or kills microorganisms. Strictly speaking, the term antibiotic should be reserved to describe natural compounds produced by organisms that kill or inhibit other organisms (usually bacteria), but the terms antimicrobial, antibiotic and antibacterial are often used interchangeably. Antimicrobial prophylaxis (perioperative antibiosis) refers to the administration of antimicrobials in the period immediately before, during and potentially for a limited time after a surgical procedure (usually no more than 24 hours). This chapter addresses Wound infection; Antimicrobial drugs; Rational approach to antimicrobial prophylaxis; and Therapeutic use of antimicrobial agents in the surgical patient.