Bispectral index (BIS) monitoring may assist reduction in utilisation of anaesthetic agents during general surgical procedures. This study was designed to test whether the use of BIS monitoring reduces the anaesthetic requirements during off-pump coronary artery bypass grafting (CABG). This prospective - clinical trial was conducted on 40 adult patients undergoing elective off-pump CABG. Patients received either isoflurane or propofol anaesthesia. BIS monitoring, which guided the dose of anaesthetic, was carried out in 50 percent of the patients. The amount of anaesthetic agent (isoflurane or propofol) administered from the start of anaesthesia to the end of surgical procedure was calculated and were compared in four groups of patients - namely Group A (I-no BIS) received isoflurane; end tidal concentration was maintained at 1-1.2% in a low flow technique throughout the procedure, Group B (I-BIS) received isoflurane in a low flow technique; inspired concentration was dictated by BIS value maintained at 50; Group C (P-no BIS) received propofol at a dose range of 4-8 mg/kg/hr and in Group D(P-BIS) the propofol infusion rate was dictated by BIS value maintained at 50. The quantity of isoflurane was significantly less for Group B (I-BIS) as compared with Group A (I-no BIS) (37 +/- 4 vs. 24 +/- 4 ml; p< 0.05) and similarly the amount of propofol infused was significantly less in Group D (P-BIS) as compared with Group C (P-no BIS) (176 +/- 9 vs. 120 +/- 6 ml; p< 0.05). BIS guided anaesthesia reduces the anaesthetic agent required for the performance of off-pump CABG. This can be extrapolated in terms of saving agent and reduced cardiac depression during off-pump CABG.