We show that a broad class of visual illusions including illusory motion can be explained by the effects of negative afterimages. Two new illusions, illusory shading and illusory tilting, are devised based on the proposed explanation. The general feature of these illusions is an alternation between a high-contrast (white or black) and low-contrast (gray) local input signal, which can be caused either by eye motion over patterns of varied luminance or by such patterns changing over time. A simple model of the local signal dynamics qualitatively reproduces the illusory effects by adding the negative afterimage to the original visual stimulus.