In this study, the author explored the relations of 2 work stressors (work overload and job insecurity) to employee alcohol use and illicit drug use. The primary goal was to explore the importance of temporal context (before work, during the workday, and after work) in the assessment of substance use compared with context-free (overall) assessments. Data were collected from a national sample of U.S. workers (N = 2,790) who took part in a broad cross-sectional survey on workplace health and safety. Consistent with past research, the results fail to support a relation between work stressors and overall measures of alcohol and illicit drug use. However, the results support the relation of work stressors to alcohol and illicit drug use before work, during the workday, and after work. These results provide support for both the stress-induced substance use and stress response dampening propositions of the tension-reduction hypothesis. When exploring the work environment as a potential cause of employee substance use, these results underscore the importance of measures that assess alcohol and illicit drug use in terms of their temporal relation to the workday.