This study employs a developmental model (Hser, Longshore, Anglin, 2007) for mapping alcohol- and drug-using careers, following in the tradition of work done by Blomqvist (1999). Based on a rolling sample of 269 former alcohol and heroin addicts, initially reported by Best, Ghufran, Day, Ray, Loaring (2007), this article examines differences in trajectories of careers among problem substance users and examines reasons for achieving and maintaining desistance, based on three groups: primary drinkers (n = 98), primary heroin users (n = 104), and those who reported problems with both alcohol and drugs (n = 67).Former heroin users reported more rapid escalation to problematic use but much shorter careers involving daily use than was the case in the alcohol cohort. Alcohol and heroin users also differed in their self-reported reasons for stopping use, with drinkers more likely to report work and social reasons and drug users more likely to report criminal justice factors. In sustaining abstinence, alcohol users were slightly more likely to report partner support, while drug users were more likely to report peer support and were also more likely to emphasize the need to move away from substance-using friends than was the case for former alcohol users. Users of both alcohol and heroin were least likely to cite partner factors in sustaining recovery but were more likely to need to move away from using friends and to cite stable accommodation as crucial in sustaining abstinence. Career factors would appear to vary across substance types, with multiple-substance users having trajectories that share characteristics with the primary users of each substance. Poly-drug use patterns have significant implications for our understanding of addiction careers and desistance patterns.