75 patients were randomized to study the analgesic effects of preemptive and preventive acetaminophen use against a placebo treatment in lower extremity surgery. Patients were allocated into 3 groups: preventive acetaminophen administration before skin closure, preemptive acetaminophen administration a half hour before surgery, and a control group. Postoperative results showed lower Verbal Rating Scale pain scores for acetaminophen groups at 6 hours, as well as lower analgesic consumption at 24 hours, especially for preemptive group. Time to analgesic requirement was longer for both experimental groups.