Infections represents 5% of our post-operative morbidity and result in the use of expensive antibiotics and longer hospital stays. As a less expensive alternative to systematic antibiotherapy for all patients, the authors propose a prospective and descriptive study of the effectiveness of antibioprophylaxis by administering 1 g of Cefotaxime pre-operatively. The study concerns a continuous series of 103 cases in gynaecology and obstetrics operated in the Dakar University Teaching Hospital, during a 13 months period (April 95-April 96). The average age of the patients is 30 years, the major types of surgery was cesarean sections, laparotomy for extra-uterine pregnancy and myomectomies. The duration of the surgery varied between 40 to 105 minutes with an average of 60 minutes. There was no intolerance to Cefotaxime. No cases of post operative infections were observed. All surgical wounds healed in 6 to 8 days except 2 minor cases of non-union of 1 cm. Antibioprophylaxis with Cefotaxime can therefore be considered as an effective means of preventing post-operative infections in clean surgery. It is easy to administer and also has the advantage of lower cost (4050 Fcfa compared to 29,000 Fcfa for classic antibiotherapy).