BACKGROUNDModified Radical Mastectomy (MRM) is the most common surgical procedure for operable breast malignancies. Postoperative pain has been severe in MRM cases and demands for pain relief are high. The technique of performing pectoral nerve block [PECS] using ultrasound guidance is increasing in popularity. We compared the postoperative analgesic profile of ultrasound-guided serratus plane block (SPB) and landmark-guided paravertebral block (PVB). MATERIALS AND METHODSThis study was done as a double blind, randomised, controlled trial among 60 subjects with breast cancer posted for elective MRM, of which 30 subjects were put in PECS block group and 30 subjects in paravertebral block group. PVB was performed under complete aseptic precaution with low resistance technique. PECS block was performed in supine position with the U/S probe directly above 1 st rib where pectoralis major and pectoralis minor muscles are located. Anaesthesia was maintained with sevoflurane 1% and O2/N20 mixture with a fraction of 50% inspired O2. Postoperative pain was recorded using the Visual Analogue Scale (VAS) every one-hour up to 4 hours post-surgery. RESULTSThe mean VAS scores were significantly lesser in the PECS group compared to the PVB group (p<0.05). The mean heart rates in PECS group were significantly lower than PVB group throughout the procedure. There was no significant difference in the intra-OP MAP between both the groups. CONCLUSIONUltrasound-guided PECS block is an alternative analgesic technique to thoracic PVB for postop pain relief in MRM patients. It gives superior analgesia and has fewer complications. BACKGROUND Breast cancer has emerged as the most common cancer in India, and 2 nd most common even in the rural area. Breast cancer accounts for 25% to 32% of all female cancers in all these cities. This implies, practically, one fourth of all female cancer cases are breast cancers. [1] Of the several therapeutic options for breast cancer, Modified Radical Mastectomy (MRM) is the most common surgical procedure for operable breast malignancies. Postoperative pain has been severe in MRM cases and demands for pain relief are high. KEYWORDS