Purpose: In this prospective, randomized, double-blind study, our aim was to compare the analgesic efficacy of the semi-blind approach of transversus abdominis plane (TAP) block with a placebo block in patients undergoing unilateral inguinal hernia repair. Methods: After receiving hospital ethical committee approval and informed patient consents, American Society of Anesthesiologists (ASA) I-III patients aged 18-80 were enrolled in the study. Standard anesthesia monitoring was applied to all patients. After premedication, spinal anesthesia was administered to all patients with 3.5 mL heavy bupivacaine at the L3-L4 subarachnoid space. Patients were randomly allocated into 2 groups. Group I (n = 32) received a placebo block with 20 mL saline, Group II (n = 32) received semi-blind TAP block with 0.25% bupivacaine in 20 mL with a blunt regional anesthesia needle into the neurofascial plane via the lumbar triangle of Petit near the midaxillary line before fascial closure. At the end of the operation, intravenous (IV) dexketoprofen was given to all patients. The verbal analog scale (VAS) was recorded at 2, 4, 6, 12, and 24 hours postoperatively. Paracetamol IV was given to patients if their VAS score. 3. A rescue analgesic of 0.05 mg/kg morphine IV was applied if VAS. 3. Total analgesic consumption and morphine requirement in 24 hours were recorded. Results: TAP block reduced VAS scores at all postoperative time points (P, 0.001). Postoperative analgesic and morphine requirement in 24 hours was significantly lower in group II (P, 0.01). Conclusion: Semi-blind TAP block provided effective analgesia, reducing total 24-hour postoperative analgesic consumption and morphine requirement in patients undergoing elective unilateral inguinal hernia repair. © 2013 Salman et al, publisher and licensee Dove Medical Press Ltd.