Knowledge of the influence of situational variables and the importance of interaction between person and situation requires a more complex view of illness than that held by many practitioners of psychosomatic medicine, who attribute causality solely to internal and isolated personality traits. Personality was studied, therefore, as a conditioner of the effects of stressful life events on illness onset in three professional groups: business executives, lawyers, and Army officers. Similarities and differences in general stress resistance and personality mediation emerged. In each case, the personality traits of commitment and control functioned to heighten resistance to the effects of stress. A powerful correlation between stress and physical illness was found for Army officers, but not for lawyers. The personality trait of challenge tended to increase officers' illness scores and to decrease lawyers' and executives' symptoms. These differences can be explained by a model that looks at personality in conjunction with stressful life events and the distinctive structures and processes of each specific profession. (Author/CS)