Generally, State traffic officers work independently, patrolling highways to enforce State traffic laws. Sheriffs' deputies work more interdependently in county jails, courts, and on patrol. Study subjects consisted of 249 graduates from 1 of 2 agency-affiliated municipal sheriff's academies and 442 from a highway patrol academy. On the first day of training, all classes were administered a battery of psychological tests that included the Minnesota Multiphasic Personality Inventory and the California Psychological Inventory. Results indicate that both officer groups have common personality characteristics that distinguish them from the general population. Both officer groups are psychologically defended, energetic, competitive, dominant, independent, achievement-oriented, spontaneous, flexible, and socially ascendant. Both groups consist of well-adjusted persons who subscribe to a traditional work ethic and show leadership potential. Deputies tended to score higher on the aforementioned variables and show less personality variations across the group. Traffic officers showed a greater range of personality variation and were somewhat more representative of the general population. Implications are drawn for the selection of law enforcement personnel for different agencies. 5 tables and 10 references.