A nationwide comparative study of the 677 sites using DISCOVER or SIGI (computer-assisted career guidance systems) as of June 1984 was made. Software-based and institutionally-based factors influencing system use were explored. The former included theoretical bases, ease of software usage, and developer's implementation assistance; while the latter included staff competence, organizational dynamics, financial resources, clientele, implementation plan, and system integration with other activities and facilities. The sample included 408 respondents (60 percent of the 677 DISCOVER and SIGI sites surveyed). Multivariate log-linear models were used to analyze data in five areas of systems use, and univariate analyses were used in two other areas. Results suggested that institutionally based factors, not software-based factors, were largely determining how DISCOVER and SIGI were used. However, it was noted that software-based factors, such as system theory bases, might be emphasized more by researchers, developers, and practitioners in order to maximize the impact of computer-assisted career guidance systems. (The report includes 10 tables and the survey instrument.) (KC)