The incidence of infection in neurological surgery is analysed by the author due to an almost epidemic occurrence of wound contamination by straphylococcus aureus in the year 1977. A brief review of the literature data is presented concerning the factors related to the patient's own immunity, the operative wound and the hospital environment, that may cause infection. Based on 733 operations done in a period of 50 months the author exposes the modifications installed for avoiding the infective sources. Antisseptic technic and surgical tactic were modified during the three steps of this study. In the firts two periods, each of one lasting 17 months, the infection rates for clean surgical procedures were 10,3 and 6,7% respectively. By the last 15 months, when topical oxacyllin powder was added, the infection rate droped to 0,6%. The general infection rates for clean, clean with iimplants, clean-contaminated and contaminated operations, during the three periods were 7,08, 6,8 and 3,4%. A critical review of the data concerning to systemic and topical prophylactic antibiotic therapy is followed by comments on the basis of the technical changes made in this clinical study. Shaving close to the operation, dry preparation of the scalp flap and muscle, use of only bipolar coagulation, restrict use of serum irrigation during the epidural stages of the operation an topical use of oxacillin powder before wound closure were the main technical modification introduced.