Two studies investigated the relation of lightness perception to the perception of spatial position. The results confirm earlier findings that lightness perception may be affected by how an O perceives the surface to be oriented with respect to the illumination. The results fail to support the hypothesis, however, that the ap-paretn position of a surface relative to the illumination is used as a basis for computing the albedo of a surface. Rather, the general hypothesis the studies appear to support is that processes of perceptual organization come into play as a result of the cue properties of stimuli which affect whether a variation in luminance will be seen as a difference in the illumination of the surface or as a difference in the lightenss of the surface. Thus, an area of reduced surface luminance seen in one position as a shadow is, in another, seen as a gray surface color, in each case consistent with the apparent position of the surface.