Methadone treatment for heroin addiction has followed three distinct periods in Geneva, Switzerland. The first period (1970-1979) corresponds to the beginning of the heroin addiction epidemic. Treatment was restricted to detoxification and did not succeed in reducing fatal overdoses. During the second period (1980-1989), methadone maintenance program was favoured but access to this program was limited. This period has brought a decrease of illegal heroin consumption and criminality but not of fatal overdoses. Finally, during the third period (since 1990), legislation was changed to allow easier access to methadone maintenance program. As a consequence there was a significant drop in lethal heroin overdoses and in deaths attributed to HIV.