The injection of illicit drugs and the epidemic of human immunodeficiency virus (HIV) infection to which it contributes are still public health challenges in China.1 Methadone maintenance treatment (MMT) has become a critical component of broader harm reduction strategies focused on the harms of dependence on illicit drugs, HIV infection and acquired immunodeficiency syndrome (AIDS), and infection with hepatitis C virus. MMT programmes have been credited internationally with several important effects, which include reductions in illicit drug use and high-risk drug-related behaviour, in the incidence and prevalence of HIV infection and in the incidence of hepatitis C virus infection.2–5 As a result, China has rapidly scaled up MMT nationwide – from eight clinics serving about 1000 clients in 20046 to 738 clinics that had already served over 340 000 clients cumulatively as of the end of 2011. No other country has successfully expanded MMT services in such a short time or to such a degree, and China’s National Methadone Maintenance Treatment Programme is now recognized as the largest single opioid agonist maintenance treatment programme in the world.