Aims and Objectives: The present study entitled “Effect of addition of Dexamethasone to Local Anaesthetic agent in Supra clavicular Brachial plexus block: A Comparative study” is undertaken with the following aims & objective: i) Onset of action, ii) Onset of sensory blockade, iii) Onset of motor blockade, iv) Motor block regression, v) Duration of analgesia, vi) Untoward side effects Study Design: A prospective, randomized, comparative study consisting of 30 patients in Group A and 30 patients in Group B Materials and Methods: 60 patients admitted to M.Y. Hospital attached to Mahatma Gandhi Memorial Medical College, Indore undergoing upper limb surgery lasting more than 90 minute were included in the study. The elective surgical interventions were internal fixation of bones with plates and screws, excision of bone cysts, reconstructive and other surgeries involving upper limb. The anaesthetic procedure to be carried out was explained. They were informed about development of paresthesia written informed consent was taken. They were educated regarding the visual analogue scale. Basic laboratory investigations were conducted including haemogram, urine analysis and whenever needed chest x-ray, electrocardiogram, blood sugar. Serum creatinine, blood urea. Method of collection of data: Supraclavicular brachial plexus block was carried out as an elective procedure on the patients undergoing upper limb surgery. Sixty patients were randomly allocated into two groups (group A, n=30 and group B, n=30) in double blind fashion. All drugs solutions were prepared by an anaesthesiologist not involved in administration of anaesthesia, patient care and data collection. Group A (n=30): Received brachial plexus block with 2% lignocaine with adrenaline at the dose of 14 ml and 0.5% bupivacaine 16ml to the solution. Group B (n=30): Received brachial plexus block with 2% lignocaine with adrenaline 14 ml and 0.5% bupivacaine 16ml 2mg/kg along with dexamethasone 4mg into the solution. All the necessary equipments and drugs needed for administration of general anaesthesia and for resuscitation were kept ready in order to manage in case of failed block or toxic reactions occurring during the procedure. The effects of anaesthetics on the following parameters were observed; Onset of analgesia: 1) Time of onset for sensory blockade, 2) The duration of sensory blockade, 3) The duration of analgesia, 4) Quality of motor blockade, 5) Tourniquet tolerance, 6) Sequelae & complication Post operative assessment: Patients would be evaluated post operatively, every hourly for first six hours, second hourly for next twelve hours, for the following parameters -intensity of pain, motor and sensory recovery. Patients were also monitored for the side effects of dexamethasone. Statistical Analysis Used: Chi-Square and Fisher Exact test has been used to find the homogeneity of sex distribution between the two groups and student t test has been used to find the homogeneity age and weight distribution between the two groups. Student t test (Two tailed) has been used to find significant difference of hemodynamics between the two groups and the study parameters namely, Time of onset, duration of surgery, duration of motor and sensory blockade and duration of analgesia between the two groups. Mann Whitney U test has been used to assess the significant difference of VAS score between the two groups. Chi-Square and Fisher Exact test has been used to find significant difference of incidence of side effects between the two groups. The statistical software used were SPSS. 12.0.1 for windows and statistics. Results: There was statistical significance in terms of onset, sensory blockade, motor blockade and duration of analgesia between the two groups. However the average duration of analgesia were 5.28±0.58hrs and 16.38.±0.29hrs in groups A and B respectively, showed statistical significance. The group B showed prolonged analgesia produced by addition of dexamethasone to local anaesthetics. Conclusion: The randomized comparative study of Brachial plexus block with local anaesthetics, with and without Dexamethasone has revealed that postoperative analgesia has been found to be significantly prolonged in the Dexamethasone group and can be used safely.