Background: Brachial plexus blockade for upper limb surgeries is the most common major peripheral nerve block technique and a significant difference exists between the onset times of various agents when these blocks are used. Adjuvants are added to improve the quality of anaesthesia and the duration of post­operative analgesia. The study was aimed to compare the addition of potassium chloride to bupivacaine in supraclavicular brachial plexus block and to assesss the onset of blockade – sensory and motor blockade, duration and quality of sensory and motor blockade. Methods: Sixty patients of age group between 18 and 60 years with ASA grade I and II, were selected for the study . Each patient was randomly assigned to one of the two groups of 30 patients each, group I or group II. Group – I was bupivacaine who received 30 ml of 0.375% bupivacaine. (control group) and group – II received 30 ml of 0.375% bupivaccine with 0.2 mmol of potassium chloride (prepared by adding 0.1ml of potassium chloride and 10 ml of normal saline to 20ml of 0.5% bupivaccine). (Study group). Both group were compared with respect to onset, duration and quality of sensory and motor blockade. Results: The onset of sensory and motor blockade was early in study/potassium group when compared to plain bupivacaine group. The duration of blockade was prolonged in study/potassium group when compared to other group. However, the quality of sensory blockade was better in potassium group when compared to other group. But the quality of motor blockade was similar that of plain bupivacaine group. Conclusion: Addition of potassium to bupivacaine when compared to plain bupivacaine is beneficial in supraclavicular brachial plexus blockade .