A study was conducted to derive an Occupation Analysis Inventory (OAI) based hierarchical occupational cluster structure which could provide the framework and content for developing an information system applicable to occupational exploration and guidance. (The OAI is an instrument containing 622 work elements which are descriptions of work activities and conditions on which jobs and occupations are rated.) A sample of 1,414 jobs was profiled on 102 selected OAI first-order work dimensions and a pairwise job similarity matrix was computed. A hierarchical cluster analysis produced twenty-one macro clusters which subsumed eighty-eight micro clusters. Subsequent modifications of the structure expanded the major clusters to twenty-five and reduced the micro clusters to forty-seven. Statistical analyses of the macro clusters showed moderate to substantial within-cluster homogeneity, intercluster discriminability, and cluster stability. (In addition to some data analysis tables, the appendix includes a description of an envisioned OAI-based information system, profile variables for 1,414 jobs, homogeneity index to identify clusters, the jobs and work-dimensions profiles of the macro clusters, macro cluster profiles on 102 attributes, jobs within the micro clusters, and relationships among products and work units in an individualized vocational information system.) (Author/EM)