This causal-comparative study examined reported practices by principals when hiring assistant principals. Two hypotheses were under investigation. The first hypothesis was "Principals will hire assistant principals with similar characteristics rather than hire assistant principals with dissimilar characteristics," and the second hypothesis was "Principals who use structured interviews to hire assistant principals will hire assistant principals with dissimilar characteristics more often than principals who use unstructured interviews to hire their assistant principals." Over 100 principals and their assistant principals from three school districts were invited to participate. Sixty-three principals and 67 assistant principals participated in the study. The responses from 48 matched pairs of principals and their assistant principals were used to investigate the hypotheses. All participants were asked to complete two Big Five personality inventories. Principals answered the questionnaires about themselves, and then they answered another questionnaire about their assistant principals. Assistant principals answered questions about themselves, and on the second questionnaire, they answered the questions based on how they thought their principals perceived them. Similarity index scores were created for the Big Five personality traits and demographic characteristics, and the responses to the interview format used by principals provided data for the analyses. The independent variables were the type of interview (structured or unstructured) and whether the assistant principal was hired by the principal. The dependent variables were the Big Five Inventory similarity indexes and the demographic similarity indexes. No statistically significant differences were found among the similarity indexes. In each comparison made between the principal/assistant principal pairs, the average personality indexes were low, indicating that the principal/assistant principal pairs were similar in personality; however, the demographics similarity index was high, indicating pairs were not as similar in demographics as they were in personality. No statistically significant differences in principal/assistant principal similarity index scores and the demographic similarity index scores of the comparisons between the types of interview used and if the principals hired the assistant principals were found. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]