The Office of the Under Secretary of Defense for Intelligence funded the Defense Personnel and Security Research Center to assess whether expanding psychological screening to include all DoD applicants could prevent future insider attacks. In furtherance of this goal, researchers conducted a literature review and interviewed subject matter experts (SME) in psychological assessment, screening, and insider threat. Overall, although the literature and SMEs suggested that individual predispositions (i.e., personality traits, emotional issues, social skills deficits, and mental health symptoms and diagnoses) are relevant to the risk of insider attacks, and several organizations model effective screening programs, findings here suggest that large-scale implementation of psychological screening for DoD applicants is premature due to a number of considerations. First, psychological assessment of relevant personality and mental health characteristics requires significant expertise, time, money, and labor to administer effectively. Second, due to the high-stakes context, it is likely that applicants will misrepresent their responses. The authors recommend that any expansion of psychological screening in DoD should focus only on the highest risk groups, and any screening process should include an assessment of response validity to account for deception. DoD also should carefully consider the side effects of additional screening on the future applicant and current employee populations prior to any significant expansion.