The authors report the results of a three-year longitudinal study of retention among undergraduate engineering students enrolled at four major universities. The study demonstrates that self-efficacy can be a critical factor in student persistence and can be broken down into three components: work, career, and academic self-efficacy. The authors explain the relationship between two of these forms of efficacy and retention and also explore the contributing roles of gender, academic support, and work experience along with its accompanying instruction. Of note, both the quantity and quality of co-op placements in addition to efficacy and support were found to sustain collegiate persistence.