The present paper describes the theory of vocational interests by J. L. Holland (1997) with respect to psychological counseling. Holland's theory of vocational interests differentiates between six vocational interest dimensions (Realistic, Investigative, Artistic, Social, Enterprising, and Conventional; "RIASEC-model"). Recent developments with respect to the assessment of vocational interests and regarding further theoretical developments of the model are described. Additionally to interest questionnaires, nonverbal tests and objective personality tests are discussed as well. Popular interest inventories that are based on this model provide code-lists that can be used to describe the congruency of the client's interest structure with a specific vocation in a three-letter code (according to the highest scores). A new theoretical development is to give feedback not only congruency with occupations but as well on the congruency of the interest profile with vocational activities. This approach is described in detail. Concluding, a recapitulating reflection on drawbacks and opportunities of the use of the theory in psychological counseling is given.