A series of experiments were carried out to study effects of luminance gradient on the luminance limit of surface-color mode perception. A CRT monitor displayed the stimuli which had a upward or downward luminance gradient. We tested several gradient directions of the test stimulus placed in the surrounding stimuli, and two configurations of the mondorian-type surrounding stimuli. The observer adjusted luminance of the test color so that it just began to appear partially in aperture-color mode. Our results indicated that the upper-limit luminance of test stimulus tend to be the same regardless of the presence of the luminance gradient. When the test stimulus had the luminance gradient in the direction opposite to that of the surrounding luminance gradient, the upper-limit luminance was lower. It is suggested that the brightest stimulus in the surrounding stimuli does not necessarily work as a cue for the judgment of color appearance mode, but the visual system discounts the illumination gradient to see a surface color.