This study investigates trajectories of heroin use and subsequent consequences in a sample of 471 male heroin addicts who were admitted to the California Civil Addict Program in 1964-1965 and followed over 33 years. Applying a two-part growth mixture modeling strategy to heroin use level during the first 16 years of the addiction careers since first heroin use, the authors identified three groups with distinctive profiles: stably high-level heroin users (n = 278), late decelerated users (n = 149), and early quitters (n = 44). Study findings empirically demonstrate the chronic nature of heroin addiction and subsequent adverse consequences including mortality, mental health, and employment. (Contains 4 tables and 1 figure.)