Nicorandil is usually considered to be a potent antianginal agent characterized as a potassium channel opener. It has been suggested that it may exert similar action on cerebral vessels. We administered nicorandil to surgical patients under general anesthesia. While the regional cerebral oxygen saturation (rSO2) and blood volume index (BVI) were determined continuously, each patient received the drug at dose of 0.08 mg.kg-1.h-1 initially, and after 15 minutes, the dose was increased by 0.08 mg.kg-1.h-1 at a time. This was repeated until the dose reached 0.40 mg.kg-1.h-1. At every dose level, rSO2 and BVI were determined, and the dose-response relationship was obtained. We found that nicorandil also produces cerebral arterial dilation under clinical conditions.