Four null hypotheses were formulated to test for relationships between pairs of identical and fraternal twins and their parents on measures of locus of control. Two additional hypotheses were formulated to test for differences between mean scores of identical and fraternal twins and scores of their parents on these same constructs. Twenty pairs of 6-year-old identical twins and 20 pairs of same-age fraternal twins were administered the Stanford Pre-School Internality-Externality Scale (SPIES), while their parents were administered the Reid-Ware Internality-Externality Scale (RWIES). Pearson r correlations were calculated to test for similarities within the twin pairs, between the identical and fraternal twins, and between parents and twins. Group differences between pairs were determined by the t test. Results indicated significant relationships for fraternal twins on SPIES, as well as relationships between mothers' scores on RWIES and identical twins' scores on SPIES. No interpair relationships for fraternal twins were found. Based on these results, it was concluded that identical twins have different conceptions of their ability to control their world and that fraternal twins perceive their ability to control their world similarly. Further, a differential relationship was found to exist between the mother's internality orientation and the orientations of dominant (external) and nondominant (internal) twins. (MP)