Local anesthetic infiltration may reduce postthyroidectomy pain. We performed a double-blinded, randomized, placebo-controlled trial to assess the analgesic efficacy of bilateral superficial cervical plexus blocks performed at the end of surgery. Ninety patients undergoing elective thyroid surgery by the same surgeon under general anesthesia were randomized to receive 20 mL isotonic sodium chloride or 20 mL bupivacaine 0.25% with 1:200,000 epinephrine. Postoperative pain was assessed every 4 h using an 11-point numeric rating scale (NRS-11). All patients received acetaminophen every 6 h. In addition, morphine was administered following a standardized protocol if the NRS-11 score was > or = 4. The main outcome variables were pain scores (NRS-11), the proportion of patients given morphine at any time during the 24-h period, and the amount of morphine administered. The Bupivacaine group had a smaller proportion of patients given morphine (66.0% vs 90.0%; P = 0.016), and lower initial median pain scores (P = 0.002). We conclude that bilateral superficial cervical plexus blocks significantly reduce pain intensity in the postoperative period after thyroid surgery but do not provide optimal pain relief alone.