This study assessed hemodynamic changes associated with alcohol intake in people who have different sensitivities to alcohol due to an inactive form of mitochondrial aldehyde dehydrogenase (ALDH). People with ALDH2*1/*2 are more sensitive to alcohol than people with ALDH2*1/*1. Six ALDH2*1/*1 subjects and four ALDH2*1/*2 subjects participated in this study. The subjects drank whisky with water (0.4 ml/kg of ethanol). Optical topography (Hitachi Medical Corporation: ETG-100) was used to measure hemodynamic changes in an occipital region during visual stimulation. Hemodynamic changes, heart rate, mean blood pressure, and reaction time were measured 20 min before, immediately after, and 20, 40, and 60 min after alcohol intake. Breath-alcohol concentration was measured at each of the assessment points. After alcohol intake, the hemodynamic peak value, peak time, reaction time, and heart rate of the ALDH2*1/*2 subjects differed from those of the ALDH2*1/*1 subjects. The hemodynamic peak value and reaction time gradually increased 60 min after alcohol exposure, and the peak time was shortest 20 min after alcohol intake. These results might reflect different acetaldehyde levels causing changes in the reactivity of the vascular smooth muscle and cerebral activity in the visual cortex.