China's methadone maintenance treatment program was initiated in 2004 as a small pilot project in just eight sites. It has since expanded into a nationwide program encompassing more than 680 clinics covering 27 provinces and serving some 242 000 heroin users by the end of 2009. The agencies that were tasked with the program's expansion have been confronted with many challenges, including high drop-out rates, poor cooperation between local governing authorities and poor service quality at the counter. In spite of these difficulties, ongoing evaluation has suggested reductions in heroin use, risky injection practices and, importantly, criminal behaviours among clients, which has thus provided the impetus for further expansion. Clinic services have been extended to offer clients a range of ancillary services, including HIV, syphilis and hepatitis C testing, information, education and communication, psychosocial support services and referrals for treatment of HIV, tuberculosis and sexually transmitted diseases. Cooperation between health and public security officials has improved through regular meetings and dialogue. However, institutional capacity building is still needed to deliver sustainable and standardized services that will ultimately improve retention rates. This article documents the steps China made in overcoming the many barriers to success of its methadone program. These lessons might be useful for other countries in the region that are scaling-up their methadone programs.