With a concentric-circular pattern, the innerr circle being the test field (TF) and the surrounding ring-shaped area being the inducing field (IF), the amount of over-or under-estimation of size and lightness of TF were measured. The difference in depth between TF and IF (from 0m to 5m) and the size of IF were varied. TF of midgray was presented either in front of or behind IF. IF was black in one condition and white in the other. The results showed that neither Morinaga's assimilation-contrast hypothesis nor Gogel and Mershon's depth adjacency principle can explain the present findings adequately. The possibility of applying some modified form of Coren's figure-ground hypothesis was discussed.