We analyze long-term trends in past-year hallucinogen use among veterans as compared to nonveterans. This topic is theoretically strategic because the military adopted stringent and successful antidrug policies in the mid-1980s, which serves as a natural experiment to examine the potential long-term impact of comprehensive drug policies on illegal drug use. Drawing on self-reported data from the National Survey of Drug Use and Health in years 1985, 1988, and 1990–2010, the analysis uses age-period-cohort analysis to update trends in past-year hallucinogen use and to examine the impact of veteran status. Results are consistent with the hypothesis that a stringent antidrug policy can lead to a life-long reduction in hallucinogen use. Among birth cohorts who were young adults immediately before the implementation of the antidrug policies (those in the 1960–1964 birth cohort) odds of past-year hallucinogen use were twice as high for veterans as compared to nonveterans over the life course. This difference disappeared among birth cohorts that were young adults after the antidrug policies were implemented, when the prevalence of past-year hallucinogen use would be expected to be higher for veterans because of their significantly higher rates of illegal drug use in adolescence. After the drug-testing policies were implemented veterans actually had significantly lower prevalence of past-year hallucinogen use in comparison to nonveterans among the subgroup of respondents who reported a history of illegal drug use before age 18 (OR = .77, p < .01). These trends across veterans and nonveterans were not explained by trends in recruits’ tendencies for illegal drug use. These findings point to service in today's armed forces as a turning point that, overall, leads to a lasting, lifelong reduction in substance use.