A refined and quantitative investigation of an earlier study which demonstrated that a line seen as tilted somewhat from the vertical or horizontal axis appears less tilted during the course of perception. Evidence from the present experiments reveals that the degree of adaptation toward the vertical and horizontal increases with longer and longer periods of inspection in a time curve similar to those of other processes of adaptation. The tilt-adaptation is never complete, however, but levels off before the quality of tilt is completely eliminated. In another phase of the present investigation it was shown that a negative after-effect on one reference-axis is accompanied by a corresponding indirect effect on the other axis, less in amount than the direct effect. The question as to whether simultaneous contrast between neighboring regions of the visual field can be shown to operate in the perception of tilt is postponed for subsequent treatment.(PsycINFO Database Record (c) 2016 APA, all rights reserved)