Officials employed in the criminal justice system have a duty to serve, protect, and uphold the law. Nevertheless, previous research has found problematic drinking and illegal substance use exists among criminal justice system employees. Criminal justice employees may be more likely to use substances due to strains or due to increased access to drug. On the other hand, self-selection and screening processes may result in a pool of employees who fewer substances than the general population. Using waves 1 through 17 of the National Longitudinal Survey of Youth 1997, the current research examines substance use patterns of criminal justice system employees, assessing how their rate of substance use compares to a nationally representative sample, and how their substance use changes once employed with the criminal justice system, this research surveys the alcohol and illicit drug use of people who went on to work in the criminal justice system and how their substance use compares to the general population. In addition, this research compares police officer substance use to the general population. When compared to a nationally represented sample, criminal justice system employees consistently use illegal substances at lower rates. However, the prevalence of alcohol use among police officers specifically is higher when compared to the general population and increases once employed with the criminal justice system. Information from this research can be used to help agencies with employee selection procedures and employee assistance programs for current employees.