Context: Ropivacaine is a new agent introduced recently which can provide differential blockade. It has been reported to produce greater degree of analgesia at the same time producing lesser motor blockade compared to bupivacaine. Aims: To compare the postoperative analgesia between 0.2% Ropivacaine with 4 mcg/ml of Fentanyl with 0.125% Bupivacaine with 4 mcg/ml of Fentanyl in knee joint replacement surgery. Settings and design: Present study was prospective randomized study carried out at SVS Medical College, Mahabubnagar. Methods: In this double blinded prospective study, 59 patients were selected and allotted into two groups, 30 in Group R and 29 in Group B by computer based randomised selection program. Combined spinal epidural technique was performed on the patient. After the completion of the surgical procedure when the patient complained of pain; basal pulse rate, mean arterial pressure, pain scores and degree of motor blockade were noted. Statistical analysis: Data was expressed as means and standard deviation and compared by using students t test. Results: The onset of action was significantly quick with ropivacaine i.e. 5.53 min compared to 6.96 min for bupivacaine; but there was no significant difference when time and duration of peak action was studied. Modified Bromage scale was used for measuring motor blockade and it was found that motor blockade was significantly less with ropivacaine group compared to the bupivacaine group. Both the agents were found to be comparable in terms of hemodynamic parameters. Conclusion: Ropivacaine in combination with fentanyl was found to be more effective than bupivacaine in same combination.