Safety requirements of domestic stairs were studied by three different experimental methods. They were: Measurement of foot movement of the user by video camera; analysis of impact force by force platform; and energy requirements of stair climbing by heart rate. Oxygen intake on the treadmill was also measured to establish the applicability of heart rate as the estimate of energy consumption. Results suggest that minimum going should be 210 mm to assure firm support during descent; maximum rise be 180 mm to control body movement; but no limit was found from energy expenditure tests for dimensions of domestic stairs.