Background: Pre-emptive analgesia is the administration of analgesics before starting the painful stimulation to prevent the CNS sensitization, thus decreasing the post-operative pain intensity. Aim of the study was to compare postoperative analgesia in patients between pre incisional infiltration and post incisional infiltration with 0.5% ropivacaine in patients of open cholecystectomy under general anaesthesia Materials and Methods: In this prospective, observational study, 30 patients belonging to ASA I or ASA II were allocated to two groups as group a, group Beach. After conventional general anesthesia, patients belonging to group A received 2 mg/kg (20ml) of 0.5% ropivacaine infiltration before incision and patients belonging to Group B received the same as wound infiltration before closure. Injection diclofenac sodium intravenous was given as a rescue analgesia when required. Statistical analysis was done using unpaired t test. We observed pain intensity with Visual Analogue Scale (VAS) at 0, 1,3,6,8 and 12hrs, time for first analgesic requirement, total diclofenac sodium consumption. Results: Mean VAS score immediately after the surgery for group A was (3.2±1.15) significantly lower than group B (4.13±1.46, P=0.0104). First analgesic dose requirement time was longer in group A (7.5±1.5hrs) than group B (4.3±1.7hrs, P=0.0104). Total amount of diclofenac sodium required in group a (65.8±20.8mg) was less than group B (110±25.8mg). Conclusion: Pre incisional infiltration with 0.5% ropivacaine significantly decreases post-operative pain intensity and diclofenac sodium consumption. Infiltration has better effect when given pre-emtively.