23 February 2010
Holland influenced practice and research in career development bycontributing a clear theory useful in organizing information about individuals and career alternatives and for understanding

Holland's theory, assessment instruments, and intervention tools transformed the delivery of vocational assistance by counselors, schools, and impersonal mechanisms. This occurred because of the organizing power of his theory of persons and environments, the case with which the theory can be communicated to counselors and clients, and the self-directed nature of the interventions and assessments he developed. This influence on counseling is due partly to the results of a long-term program of science in the pursuit of solutions to practical problems in vocational counseling and partly to the creativity and craft of an author devoted to helping clients understand themselves, their vocational alternatives, and their career situations.

In this article, we first describe the assessment and intervention tools that Holland developed. We then relate how Holland used the opportunities in the environments he experienced over the course of his career to test and elaborate the theory over time. Finally, despite its influence on career counseling, many practitioners and researchers remain familiar only with certain parts of Holland's theory of vocational personalities and work environments. Therefore, in a final section, we provide an overall sketch of the theory to direct attention to portions of Holland's work that have practical applications in counseling, but that some counselors and researchers often overlook.