In order to clarify the conditions under which material rewards have a detrimental effect upon children's later interest in the rewarded task, the effect of a reward for drawing was measured with 24 preschool children ranging in age from 34 to 40 months. The children were grouped as high or low in initial interest on the basis of observation of time spent drawing, and half the children in each group were given an expected reward for drawing, while the other half received no reward. Time spent drawing and "quality" of drawing were measured one week and seven weeks later. The high initial interest children who received a reward lost interest when observed a week later, while the low interest rewarded children gained interest. By seven weeks both groups returned to their original levels. At the time of the reward, high interest rewarded subjects drew more drawings but of poorer quality than did the unrewarded high interest children. Low interest children who were rewarded also drew more than their unrewarded counterparts, but quality was not affected. (Author/BD)