OBJECTIVE : Inadequate pain relief after anterior cruciate ligament reconstruction affects mobility leading to development of adhesions, weakened ligament insertion and muscle atrophy. Adductor canal block for postoperative analgesia preserves quadriceps strength. The present study was conducted to compare pain free period in patients undergoing arthroscopic anterior cruciate ligament reconstruction, receiving ultrasound-guided adductor canal block with ropivacaine alone and ropivacaine with clonidine. METHODS : A prospective randomized double blinded study was conducted including sixty-three adult, ASA class I, II patients undergoing anterior cruciate ligament reconstruction. They were randomized into three groups: Group S - control group received adductor canal block with 30mL saline, Group R - ropivacaine group received adductor canal block with 30mL of 0.375% ropivacaine and Group RC - clonidine group received adductor canal block with 30mL of 0.375% ropivacaine with clonidine 1μg.kg-1. The primary aim was to compare the pain free period in patients receiving adductor canal block with ropivacaine alone or ropivacine with clonidine. The secondary outcomes were pain score at rest and movement, total analgesic requirement, sedation score and postoperative nausea and vomiting. RESULTS : The mean pain free periods were 20min, 384.76min and 558.09min for Group S, Group R and Group RC, respectively and this difference was statistically significant (p < 0.001). There was no significant difference between Group R and Group RC in terms of pain scores at rest and movement and total analgesic requirement. CONCLUSIONS : Addition of clonidine to ropivacaine in USG guided adductor canal block led to significant prolongation of pain free period though pain score at rest and movement, and rescue analgesic requirement, did not differ.