Although the significance of the structure of occupational interests is generally acknowledged, there is less agreement regarding the nature of the structure. This article first discusses the circular-hexagonal model for this structure and the problem faced by it and then describes the hierarchical model for the structure of interests, which is proposed as an alternative to the circular-hexagonal model. Studies testing the assumptions of the hierarchical model are reviewed. A comparison between the circular and the hierarchical model in 18 data sets revealed an advantage of the hierarchical model. Additional support for the hierarchical model. Additional support for the hierarchical model and the compatibility of this model with the findings of previous studies are reviewed. The relation between the way occupational interests are classified and the structure of the resulting clusters is explored. Finally, the research, theoretical, and counseling implications are discussed