This study examines the interaction of mother-son dyads as a function of mothers' and sons' locus of control and the demand characteristics of specific tasks. The subjects were 32 third grade boys from parochial schools in the District of Columbia area and their mothers. They were assigned to internal or external locus of control groups based on a median split of the distribution of their locus of control scores. Subjects were observed as they interacted during a directive and nondirective teaching task and a non-teaching task. Dependent variables that were examined included preference, time to completion, and quality of performance on the teaching task and frequency of positive and negative behavior displayed during the non-teaching task. Results indicated that mothers of external sons preferred the directive over the nondirective task, whereas mothers of internal sons displayed no differences in their level of preference for either task. In addition, external sons were found to require significantly more time to complete the non-directive task than the directive task. With regard to the non-teaching task, external mothers displayed a significantly higher frequency of positive behavior (approval, agreement, and positive affect commands) with internal than with external sons. Implications of these results and recommendations for further research are discussed. (Author/DST)