Illumination of a cross-shaped pattern composed of five black to white squares on a white background was varied over 2.6 log units. The task given to 10 Ss was to make achromatic color namings and to make numerical judgments of lightness for each of the five squares in the cross as well as the background. Achromatic color constancy was almost perfect for the region of the highest contrast ratio of surround to focal luminance and less perfect for the regions with lower contrast ratios. Lightness judgments were found to change as a curvilinear function (concave downward) for a log transformation of illumination. Linearly decreasing functions were exceptional. It can be concluded, therefore, that the theoretical claim for the generality of negative functions for lightness-illumination relationships should be reconsidered.