The authors review the published, peer-reviewed studies relevant to two questions: What psychological constructs underlie police officer suitability and fitness? and What assessment instruments provide empirically validated measures of these constructs? In addressing the second question, the authors focus on examples of research related to the most commonly used instruments in these suitability and fitness evaluations (i.e., current versions of the Minnesota Multiphasic Personality Inventory, California Psychological Inventory, Sixteen Personality Factor Questionnaire, and Personality Assessment Inventory). The discussion is limited to a review of studies published in peer-reviewed journals and pertaining only to versions of the test currently supported by the test’s publisher.