This study investigates the relationship between pre-service teachers' locus of control and an application measure of science education achievement under a high and a low structured instructional treatment. Eighty college students enrolled in an elementary science methods class were administered aptitude tests which included a measure of locus of control (the James Internal-External Locus of Control Scale). The students were taught in a high-structure format - the traditional instructor-lecture mode with large-group follow-up discussions, or a low-structure format - individual study with small-group follow-up discussions. The subject matter dealt with planning science field trips for elementary school children. The results showed that the instructional treatments were related to the locus of control measure. (Author/BB)