Background: The perfusion index (PI) is a non-invasive method that measures the monitoring and success of peripheral nerve blocks in regional anesthesia. The perfusion index (PI) is an objective non-invasive method of measuring and monitoring the success of peripheral nerve blocks. We compare the effects of interscalene, supraclavicular and infraclavicular blocks on the perfusion index, with the aim being to contribute to the decision-making process regarding the type of block to be selected for surgeries in which increased perfusion is important. Methods: Included in the study were 60 patients aged between 18 and 60 years with an ASA (American Society of Anesthesiologists) I-II risk rating who were scheduled for upper extremity surgery. An equal number of patients were applied supraclavicular, interscalene and infraclavicular blockades, and the PI was measured non-invasively using a pulse-oximetry probe on the fingers on the same and opposite side of blockade at the beginning, at the 10 th , 20 th and 30 th minutes, postoperatively and in the post-anesthetic care unit (PACU). Results: After a successful blockade of brachial plexus in all patients, a statistically significant increase in PI values was detected. Aside from the initial values, the mean rate of change in PI was significantly higher in the interscalene group than the supraclavicular and infraclavicular groups (p < 0.001). Conclusion: PI can be used as a non-invasive monitoring method for the determination of the success of a brachial plexus blockade. Based on the results of the present study, an interscalene blockade may be preferred especially for surgeries in which an increase in tissue perfusion is desired due to its perfusion-enhancing properties when compared to supraclavicular and infraclavicular blocks.