Introduction: Prophylactic antibiotics have been shown to be effective in reducing the incidence of febrile morbidity associated with surgical operations. Surgical site infections (SSI's) account for approximately 15% of nosocomial infections and are associated with prolonged hospital stays and increased costs.   Objective: To improve the outcome and to reduce the time stay at the hospital. To determine the independent risk factors for post surgical infection. To decrease the incidence of post surgical wound infection.   Study Design: An intervention randomized study.   Aim of the work: To evaluate the efficacy of prophylactic antibiotics in reducing the incidence of post surgical wound infection.   Place and Duration: Department of Obstetrics and Gynecology, Department of Surgery and Department of urology, Faculty of Medicine Al-Azhar University from January to June 2011.   Patient and Method: Three hundred patients undergoing surgical operations were enrolled in this study and classified into two groups: Group1:150 patients received parental prophylactic antibiotics, 1st dose at the time of induction of anesthesia, 2nd dose after 12hs from the surgery. Group2: 150 patients received oral antibiotics for five days postoperative.   Results: In this study ,Total 300 patients were enrolled,6 patients from group 1 developed wound infection(4%),39 patients from group 2 developed wound infection(26%) ,with prolonged stay at the hospital,2.3 days in group1, and 4.9 days in group 2.   Conclusion: The use of prophylactic antibiotics therapy is satisfactory in our surgical environment, this practice would be efficient, cost effective and prevent the emergence of nosocomial infection in developing countries.