Most research and treatment focusing on the relationship between life stress and substance use have considered stress as a unitary construct despite the fact that stressors vary in terms of temporal characteristics (short-term vs. long-term) and domains (work, health). In contrast to most stressor domains, increasing evidence suggests that health stressors may reduce the risk of initiating substance use after treatment. We separately evaluated the effect of short-term stress events (discrete date of occurrence), long-term stressors (ongoing stressors lasting 2 weeks or longer), and health stressors on posttreatment alcohol and drug use. Veterans (N=195) were assessed while receiving addiction treatment and quarterly for 1 year. The odds of initiating posttreatment substance use were 2.5 times greater for participants experiencing severe (nonhealth) long-term stressors. In contrast, participants experiencing short-term health events or severe (nonhealth) short-term events were less likely to initiate posttreatment substance use (odds ratio=.28 and .44, respectively).