During the past decade, the alexithymia construct has undergone theoretical refinement and empirical testing and has evolved into a potential new paradigm for understanding the influence of emotions and personality on physical illness and health. Like the traditional psychosomatic medicine paradigm, the alexithymia construct links susceptibility to disease with prolonged states of emotional arousal. But whereas the traditional paradigm emphasizes intrapsychic conflicts that are presumed to generate such emotional states, the alexithymia construct focuses attention on deficits in the cognitive processing of emotions, which remain undifferentiated and poorly regulated. This paper reviews the development and validation of the construct and discusses its clinical implications for psychosomatic medicine.