Background: Dexmedetomidine, an alpha–2 agonist used as an adjuvant in general anaesthesia, has anaesthetic sparing property. Aims: To study the effect of dexmedetomidine on requirement of isoflurane during general anesthesia with bispectral monitoring of depth of anaesthesia . Materials and Methods: One hundred patients were randomly divided into 2 groups of 50 each. In group F, fentanyl 2 mcg/kg was given while in group D, dexmedetomidine was given intravenously as loading dose of 1 mcg/kg over 10 min prior to induction. After induction with propofol in group B, dexmedetomidine was given as infusion at a dose of 0.2–0.7 mcg/kg/hour. Isoflurane was used as inhalation agent in both groups. Hemodynamic variables, BIS and minimum alveolar concentration (MAC) of isoflurane were continuously recorded. Statistical analysis was done by unpaired student’s t–test and Chi–square test for continuous and categorical variables, respectively. p‑value < 0.05 was considered significant. Results: The use of dexmedetomidine was associated with a statistically significant decrease in MAC of isoflurane in group D (0.759±.012) as compared to group F (0.901±0.030). Conclusion: Dexmedetomidine decreases isoflurane requirement for maintaining adequate depth of anaesthesia.