In many situations, a patch of light appears several times brighter when briefly flashed than when viewed for longer durations. This aspect of visual perception is known as temporal brightness enhancement, or the Broca-Sulzer effect. Brightness enhancement has been measured by several psychophysical methods. The magnitude of the effect is known to be influenced by such physical properties of the test target as luminance, area, and chromaticity. The proposed study intends to measure the magnitude of the brightness enhancement effect using a target of constant physical properties in conjunction with various surround stimuli appearing outside the target area. A previous experiment (Corwin & Giambalvo, 1974) demonstrated that a steady surround can greatly reduce the magnitude of brightness enhancement. In the proposed study, brightness versus duration curves will be measured for a test target of constant luminance viewed in conjunction with surround fields varying in luminance, spatial configuration, and time of appearance with respect to the test target. Similar measurements will be made on constant luminance targets whose spatial characteristics are systematically varied. The results of these experiments may help to decide among alternative explanations of the brightness enhancment effect.