Neuropsychological advances may help researchers better understand the relationship between psychological constructs. This paper proposes a neuropsychological model explaining the negative relationship between hostility and "self-awareness," which has been suggested by previous research [H. A. Demaree and D. W. Harrison (1995a) "Behavioral, Physiological, and Neuropsychological Correlates of Hostility," manuscript submitted for publication; L. H. Epstein and P. A. Cluss (1982) "A Behavioral Medicine Perspective on Adherence to Long-Term Medical Regimes," Journal of Consulting and Clinical Psychology, Vol. 50, pp. 950-971; M. F. Scheier et al. (1974) "Self-Awareness and Physical Aggression," Journal of Experimental and Social Psychology, Vol. 10, pp. 254-273]. The authors review the role of the right cerebrum in both hostility and "self-awareness"--including arousal, perceptual, expressive, and integrative processes. Using identifiable tracts in the brain, the model suggests how deficits in "self-awareness"--poor awareness of physiological arousal, natural and emotional environment, etc.--may enhance the probability of hostility expression. This model is supported by previous empirical research and provides direction for future neuropsychological investigation.