Iran has 2.1 and 1.8% of its 15-64-year-old population living with illicit substance and opioid use disorders, respectively. To address these problems, Iran has been developing a large and multi-modality addiction treatment system, spanning the time before and after the Islamic Revolution.Iran's current drug treatment scene is a combination of services, ranging from medical/harm reduction services to punitive/criminal justice programs. Included in this array of services are drop-in centers providing low-threshold harm reduction services, such as distribution of sterile needles and syringes; opioid maintenance treatment clinics providing methadone, buprenorphine and opium tincture; and abstinence-based residential centers. We will review the evolution of this system in four phases.In 1980, Iran's revolutionary government shut down all voluntary treatment programs and replaced them with residential correctional programs. The first shift in the addiction treatment policies came 15 years later after facing the negative consequences. Addiction is viewed as a disease, and new voluntary treatment centers offering non-agonist medications and psychosocial services were established. With an increased number of people who inject drugs and HIV/AIDS epidemics, in the second shift an extensive move towards harm reduction strategies and opioid-maintenance programs has been implemented to reduce HIV-related high-risk behavior. The emergence of a methamphetamine use crisis creating an increased number of socially marginalized addicted people resulted in public and political demands for stricter policies and ended in the third shift starting in 2010, with extended compulsory court-based residential programs. Currently, there is a new shift towards reducing the severity of criminal penalties for drug use/sales and promoting proposals for opium legalization.Iran's evolutionary experience in developing a large addiction treatment program in a complex combination of medical/harm reduction and punitive/criminal justice addiction treatment can be examined in its political, clinical and pragmatic context.