This article reviews the role of organizational diagnosis in managerial and organizational consultative roles. The particular contributions of Harry Levinson are highlighted. The ways in which Levinson, a pioneering clinical psychologist of work and organizational issues and a pioneering psychologist-consultant, utilized and approached organizational diagnosis are reviewed. Methods of integrating these perspectives in the day-to-day work of psychologist-managers are discussed.Of course, it is possible to be a manager who is also a psychologist and who makes little use of psychological training and background in implementing the administrative role. To be a psychologist-manager, however, assumes that one applies expertise from one's psychological training and from the psychologist's role to the day-to-day work as a manager or leader (Lowman, 1997). Psychologist-managers need to be able to think in psychological, not just managerial, concepts and principles, whether working for organizations as managers or as consultants. Although psychologist-managers cannot be exclusively organizational diagnosticians and interventionists when they are serving in the managerial or leadership roles-that would create a role conflict (Lowman, 1998;Newman, Robinson-Kurpius, & Fuqua, 2002)-they can benefit from applying their psychological expertise to the managerial role and in thinking about their roles and responsibilities from the psychological, not just the managerial, perspective. Organizational diagnosis or assessment is part of this process. In this article, I highlight the contributions of one of the premiere organizational assessors and consultants, clinical and consulting