The guidelines, developed by the American Society of Health-System Pharmacists (ASHP), the Infectious Diseases Society of America (IDSA), the Surgical Infection Society (SIS), and the Society for Healthcare Epidemiology of America (SHEA), provide a standardized approach to the rational, safe, and effective use of antimicrobial agents for the prevention of surgical site infections (SSIs). The guidelines focus on primary perioperative prophylaxis and cover preoperative dose timing, selection and dosing, duration of prophylaxis, common principles, and special patient populations. Key updates include a more specific time frame for preoperative doses (within 60 minutes before incision), expanded dosing considerations for obese patients, and new recommendations for shortened postoperative courses of antimicrobials. The guidelines also address the selection of antimicrobial agents based on their spectrum of activity, safety profile, and patient allergies. They emphasize the importance of considering local resistance patterns and institutional factors when selecting antimicrobial agents. Additionally, the guidelines discuss the impact of antimicrobial prophylaxis on bacterial flora and the risk of Clostridium difficile-associated colitis. The document also provides recommendations for patients with allergies to β-lactam antimicrobials and guidelines for drug administration and dosing to ensure adequate serum and tissue concentrations.The guidelines, developed by the American Society of Health-System Pharmacists (ASHP), the Infectious Diseases Society of America (IDSA), the Surgical Infection Society (SIS), and the Society for Healthcare Epidemiology of America (SHEA), provide a standardized approach to the rational, safe, and effective use of antimicrobial agents for the prevention of surgical site infections (SSIs). The guidelines focus on primary perioperative prophylaxis and cover preoperative dose timing, selection and dosing, duration of prophylaxis, common principles, and special patient populations. Key updates include a more specific time frame for preoperative doses (within 60 minutes before incision), expanded dosing considerations for obese patients, and new recommendations for shortened postoperative courses of antimicrobials. The guidelines also address the selection of antimicrobial agents based on their spectrum of activity, safety profile, and patient allergies. They emphasize the importance of considering local resistance patterns and institutional factors when selecting antimicrobial agents. Additionally, the guidelines discuss the impact of antimicrobial prophylaxis on bacterial flora and the risk of Clostridium difficile-associated colitis. The document also provides recommendations for patients with allergies to β-lactam antimicrobials and guidelines for drug administration and dosing to ensure adequate serum and tissue concentrations.