This study reviews benefit–cost analyses of programs designed to reduce demand for illicit drugs. Data were synthesised from 67 benefit–cost analyses of prevention, law enforcement and treatment programs. Eighty percent of the 70 separate benefit–cost ratios exceeded 1.0, indicating that savings outweighed costs among most programs reviewed. Benefit–cost ratios ranged from −18.20 to 63.32, varying substantially for different program types and populations. On average, demand reduction programs produced a return on investment of $5.40 for every dollar spent. These findings suggest demand reduction programs are generally economical.