The validity of using threshold studies as the hasis for lighting level recommendations is questioned. The performance of the eye at suprathreshold levels was investigated with sine-and sijuarewave gratings. The results of the study indicate that the behavior of the eye is significantly different at suprathreshold levels as opposed to threshold levels. For threshold studies, when contrast is plotted against luminance, the function is a monotonically decreasing function. At suprathreshold levels the function indicates the existence of a definite minimum, luminances greater or less requiring more contrast to appear subjectively equal. It is recommended that lighting levels be based on laboratory studies that appraise visual requirements and performance simulating conditions encountered in real world environments.