Cooperative education research suggests that co-op participation results in enhanced career maturity, yet little is known about the vocational behavior constructs that may produce these results. The purpose of this study was to examine the relationship between co-op work experience and career decision-making self-efficacy, an individual's confidence to successfully perform various career decision-making tasks. Another purpose of this study was to test the hypothesis that only the co-op work experience group adheres to an internal career locus of control, a belief that one can control career outcomes by exercising effort. Based on social cognitive theory (Bandura, 1986), it was hypothesized that co-op work experience would provide the greatest exposure to sources of self-efficacy information, namely performance accomplishments, vicarious learning (i.e, exposure to role models or mentors), and verbal persuasion (encouragement). Thus, college students having co-op work experience were expected to report significantly higher career decision-making self-efficacy (CDMSE) compared to college students having non-co-op work experience. Survey data were collected from 415 engineering and computer science students, sophomores through seniors, who had acquired co-op work experience or non-co-op work experience (both related and unrelated to the student's field of study or career interests). There was a 69.75% survey return rate in this (3 x 3) ex-post facto design study. One-Way ANOVAs revealed that CDMSE was significantly higher in the co-op work experience group than in the non-co-op (unrelated) work experience group at the completion of the second work term only. Also, CDMSE in the first work term was significantly higher than the second work term in the non-co-op (unrelated) work experience group. No evidence was found to support a significant cumulative effect in CDMSE. A Two-Way ANOVA revealed no significant interaction effect; however, the main effect of type of work experience was significant (p = .049) for CDMSE. No significant difference was found in the proportion of internal career locus of control between the co-op and non-co-op group. This study's findings did not support prior investigations that found a relationship between engagement in career exploration activities and an internal career locus of control. One-Way ANOVAs revealed a distinct pattern of significance among groups on work experience satisfaction, regardless of the work term completed. Though the co-op group and non-co-op (related) work experience group were comparable on work experience satisfaction, the non-co-op (unrelated) work experience group reported significantly lower work satisfaction from the single most significant work experience acquired during the college years. Survey feedback indicated that co-op students were well pleased with the opportunity to reality-test their career goals in the cooperative education program. Implications of the findings are discussed, and suggestions for future co-op research are provided. / Ph. D.