This study evaluated whether or not locus of control mediates rational-irrational beliefs. Data were generated investigating the impact of an internal-external orientation and selected demographic variables (age, race, gender, education, and occupation) on rational-irrational beliefs. Independent variables were locus of control and demographic characteristics, and the dependent variable was beliefs. Data were collected by administering the Internal-External Locus of Control Scale and the Irrational Beliefs Test to 105 state human service agency employees (81 internals and 24 externals). A one-way analysis of variance uncovered significant differences in internal and external females. In addition, there were significant differences in beliefs between internal and external subjects at different educational levels. Results support the view that internally oriented individuals maintain more rational beliefs than do externally oriented people. Nine tables present study data. (SLD)