The present study evaluated whether three dimensions underlie responses to the Strong Interest Inventory (SII; Hansen & Campbell, 1985). A multidimensional scaling analysis was applied to the responses of college students (404 women and 244 men) to 110 occupational title items in the SII. The results supported a three-dimensional structure of vocational interests. In both the male and female samples the dimensions of Data/Ideas and People/Things emerged. The third dimension was interpreted as Sex-type. We discuss the implications of this conclusion for the use of the SII, especially how the third dimension may influence the interpretation of inventory results.