Computer assisted career guidance systems were designed to combine the power of computers with career development theory to assist students in self assessment, career exploration, occupational and educational planning and decision making. Two systems used at educational institutions are DISCOVER (American College Testing Program), and System of Interactive Guidance and Information, abbreviated SIGI-PLUS (Educational Testing Service). There has been limited research examining what effect these systems have on career development in students. This study examined what effect using SIGI-PLUS had on career related attitudes, knowledge, and activity. The study also examined effects of gender, type of directions, and gender/treatment interaction on career development. Subjects were enrolled in introductory Psychology classes at Iowa State University. Participants were randomly assigned to one of three groups: treatment A (choose own pathway through SIGI-PLUS), treatment B (follow recommended pathway through SIGI-PLUS), and a control (deferred use of SIGI-PLUS). Students were pre- and posttested using the Survey of Career Development, Career Development Inventory, and Self-Assessment and Record of Career Planning Activity. Students in treatments A and B also completed a SIGI-PLUS User Evaluation. Length of treatment period was five weeks. Results showed significant effects of SIGI-PLUS use on career development attitudes and knowledge. Students using SIGI-PLUS had greater knowledge of: career planning and exploration, personal interests, abilities, information about occupations and decision making, and certainty of educational and occupational planning than the control group. There were no significant treatment effects on career development activity. Type of directions given to use SIGI-PLUS had no effect on career development. There were no significant effects of gender/treatment interactions on career development. Differences between findings in this study and past research could be attributed to operational definitions of scales/items used for the study, length of treatment period, different samples, and instrument design. Future research should address: refinement of instruments, determining the effect of length and mode of experimental treatment on career development, and the impact of guidance systems on various populations.