The visual completion is the result of the integration of fragmented contours. The contrast polarity (or contrast sign) may affect this interpolation by strengthening the completion in a direction where the contrast polarity is preserved. This chapter illustrates some manifestations of these phenomena: the alteration of the alignment of the visual units and the illusory tilt of more complex visual organization. The occurrence of basic distorting effects underlying classic illusions—such as the Frazer illusion—is discussed. It is noted that the role of the contrast polarity rule in representing a “preferential” rule does not preclude other possibilities, such as edges completion, although it renders the contour detectable to a lesser degree.