The primary purpose of this study was to examine the construct validity of a measure of contradictory behavior called the Index of Stress. The Index of Stress was derived from the differences between the Basic Behaviour scores and the Current Behaviour scores of the Personal Styles Inventory (PSI) (Kunce, et al., 1986, 1989, 1991). The second purpose of this study was to examine the personality differences between those police officers working for a state law enforcement agency and those police officers working for a municipal law enforcement agency. A review of the literature provided information about the acquisition of basic personality and current personality behaviours of individuals. Some of this information about influences of the development of basic personality were: situational influences; social influences; physiological influences. Some of the components that influenced the development of current personality as they applied to police officers were: training; the effects of family and significant others expectations; models of conflict. Central to this study was the assumption that the occupation of police officer tends to have greater degrees of occupational related stressors than other occupations. Subjects for this study were volunteers from a large midwestern state's Highway Patrol organization (N=152). The instruments selected for this research were the Personal Styles Inventory (PSI)(Kunce, et al., 1991), Beck Depression Inventory (BDI) (Beck, 1978), Schedule of Recent Life Events (LES)(Holmes and Rahe, 1967), and the PTSD Sub-scale of the MMPI (Keane et al., 1984). This study provides evidence for the Index of Stress (IS) of the PSI as a valid measure of stress. Significant correlations were found between the Index of Stress and life stress and depression. The second purpose of this study examined the personality differences between police officers working for a state law enforcement agency and police officers working for a municipal law enforcement agency. Differences were found in the ways in which these two groups of police officers cognitively viewed the world in which they exist.