Since 1992, the Belgian network for the surveillance of nosocomial infections runs a system of voluntary surveillance of surgical wound infections, including the perioperative antibiotic prophylaxis patterns. From 1992 to 1995, the global rate of prophylaxis was 71%, calculated on 44,728 interventions from 72 hospitals, but in 11.4% of operations for which prophylaxis is indicated, it was not given. On the other hand, prophylaxis was prescribed in 55.6% of operations where it was not indicated. At least 4 out of 10 courses were inappropriate with respect to indication, duration or day of administration. Fifteen percent of all courses exceeded 2 days (28% in genitourinary surgery, and 20% in abdominal surgery). In orthopedic surgery, recommended indications were not followed in 42% of operations. To improve the prescribing of antibiotic prophylaxis in Belgium, local surveillance of prophylaxis patterns and the implementation of guidelines describing good practices should be priorities at the hospital level. At the national level, recommendations about the indications for prophylaxis should be updated and disseminated.