Clinical researchers and practitioners are increasingly aware of the need for quality theory, research, and intervention in men's mental health. Successful work in this area requires an understanding of the multitude of ways that gender, and more specifically masculinities, can be conceptualized beyond a sole focus on sex differences between men and women. Drawing from a range of social sciences in addition to psychology, the authors consider several theoretical, research, and clinical directions that can follow from social learning, psychodynamic, social constructionist, and feminist paradigms. It is concluded that thinking deeply and critically within different paradigms of masculinity is critical for progress in both research and practice. © 2005 Wiley Periodicals, Inc. J Clin Psychol 61: 633–647, 2005.