Objective: The aim of this comparative double-blind, prospective, randomized, clinical trial was to evaluate two amoxicillin administration patterns. The first was a short prophylactic therapy and the second a long postoperative regimen. Study Design: The study population consisted of 160 patients who underwent mandibular third molar extraction. Patients were randomized into two equal groups. In group 1, 2 grams of amoxicillin were administered 1 hour before the procedure and 1 gram 6 hours after surgery. In group 2, patients received 1 gram of amoxicillin 6 hours after surgery followed by 1 gram every 8 hour for 4 days. All patients received the same number of tablets thanks to the use of placebo pills. A total of 25 variables were evaluated, such as alveolitis, surgical infection, number of analgesic needed, subjective pain scale, post-surgical inflammation, consistency of the diet, axillary temperature and millimetres of mouth opening loss after the surgery. Results: No statistically significant post-operative differences were found within the recorded parameters between the groups. Conclusions: Postoperative 4-days amoxicillin therapy is not justified.