This prospective, randomized, double-blind, placebo-controlled study evaluated the effectiveness of intravenous lidocaine to reduce post-operative pain in 64 inguinal herniorrhaphy patients. Intravenous bolus injection of 1.5 mg/kg lidocaine followed by a continuous lidocaine infusion of 2 mg/kg per h was randomly assigned to 32 patients (lidocaine group) and intravenous normal saline bolus injection followed by infusion of normal saline was assigned to 32 other patients (control group). Visual analogue scale pain scores, fentanyl consumption and the frequency at which analgesia was administered from a patient-controlled analgesia device (measured by number of button pushes) were significantly lower in the lidocaine group than in the control group until 12 h after surgery. Total fentanyl consumption (patient-controlled plus investigator-controlled rescue administration) and the total number of button pushes were significantly lower in the lidocaine group than in the control group. It is concluded that intravenous lidocaine injection reduced post-operative pain after inguinal herniorrhaphy, is easy to administer and may have potential to become routine practice for this type of surgery.