Students often graduate from a major other than that in which they first enrolled. A large proportion of this migration happens within engineering with students moving from one discipline of engineering to another. Some students migrate within engineering several times. While there has been extensive examination of why students leave engineering, very little research has looked into why students leave one engineering discipline for another. Longitudinal data collected from several engineering colleges has shown that there are definite trends within the movement of engineering students. This study examines the reasons for some of these trends using a unique approach which combines both environmental and personality factors. The study uses measures based on career theories such as Social Cognitive Career Theory, which has used extensively to explore vocational choice in engineering. These theories will be supplemented with measures of social influence and personality to explain disciplinary choices. In addition, this study considers the climate students are exposed to in the various engineering disciplines.