Though the basic principles of antibiotic prophylaxis have been well established, there is still considerable incorrect usage, including how much is prescribed and especially in the duration of treatment, which is generally superior to what is indicated. The adequate use of these drugs contributes towards decreasing the time of internment of the patient, prevents surgical site infection (SSI), decreasing the development of resistant microorganisms, and towards reduced costs for the hospital pharmacy. A protocol for the use of antibiotic prophylaxis in the Orthopedics and Traumatology Service of the Hospital do Servidor Público Estadual de São Paulo was developed. The objectives of the study were to promote rational antibiotic surgical prophylaxis, through the implantation of a protocol for the use of these drugs in a surgical unit, with the direct contribution of a druggist in collaboration with the Infection Control Committee, to evaluate the adhesion of the health team to the protocol during three distinct periods (daily pre-protocol, early post-protocol and late post-protocol) and to define the consumption of antimicrobials used, measured as daily defined dose.