We review evidence for effectiveness, cost-effectiveness, and coverage of antiretroviral therapy (ART) for injecting drug users (IDUs) infected with HIV, with particular attention to low-income and middle-income countries. In these countries, nearly half (47%) of all IDUs infected with HIV are in five nations--China, Vietnam, Russia, Ukraine, and Malaysia. In all five countries, IDU access to ART is disproportionately low, and systemic and structural obstacles restrict treatment access. IDUs are 67% of cumulative HIV cases in these countries, but only 25% of those receiving ART. Integration of ART with opioid substitution and tuberculosis treatment, increased peer engagement in treatment delivery, and reform of harmful policies--including police use of drug-user registries, detention of drug users in centres offering no evidence-based treatment, and imprisonment for possession of drugs for personal use--are needed to improve ART coverage of IDUs.