Objective To evaluate the efficacy of quadrates lumborum block for unilateral inguinal hernia repair in elderly patients. Methods Fifty-eight elderly patients with unilateral inguinal hernia of both sexes, aged 65-80 yr, with body mass index of 18-25 kg∕m2 , of American Society of Anesthesiolo-gists physical status Ⅱ or Ⅲ, scheduled for elective unilateral tension-free repair, were divided into 2 groups ( n=29 each) using a random number table method: iliohypogastric-ilioinguinal nerve block group (group T) and quadrates lumborum block group (group Q). Iliohypogastric-ilioinguinal nerve block with arteria circumflexa ilium profunda as a marker was carried out with 0. 33％ ropivacaine 20 ml under ultra-sound guidance in group T. The anterior approach to quadratus lumborum block was performed with 0. 33％ropivacaine 20 ml under ultrasound guidance in group Q. Operation was started after the height of sensory block was assessed by pin-prick test at 30 min after block. When the blocking effect did not meet the opera-tion requirements, an increment of 1％ lidocaine 2. 5 ml was given every time in the surgical field until op-eration requirements were met. Dexmedetomidine was intravenously infused at a rate of 0. 03-0. 07μg·kg-1 ·min-1 during surgery until the end of surgery to maintain Narcotrend index between 80 and 90. When postoperative visual analogue scale score >3, parecoxib sodium 40 mg was intravenously injected, and if marked pain relief was not found 10 min later, tramadol hydrochloride 50-100 mg was intravenously injected. The upper spread of sensory block and intraoperative requirement for additional local anesthetics were recorded at 30 min after nerve block. The requirement for parecoxib and tramadol was recorded within 48 h after operation. The development of inadvertent intravascular injection of local anesthetics, local anes-thetic intoxication and postoperative nausea and vomiting, nerve block of lower extremity and uroschesis was recorded. Results Skin pain disappeared at the plane of T11-L1 in group T and at the plane of T9-L1 in group Q. Compared with group T, the intraoperative requirement for and consumption of local anesthetics, postoperative requirement for parecoxib and tramadol, and postoperative incidence of nausea and vomiting were significantly decreased in group Q ( P<0. 05) . Conclusion Quadrates lumborum block provides bet-ter efficacy for unilateral inguinal hernia repair than iliohypogastric-ilioinguinal nerve block in elderly pa-tients.