BACKGROUND: There still are concerns about unwanted effects of harm-reduction measures that may lead to an increasing number of new heroin users. Furthermore, it is thought that the admission of a substantial proportion of heroin users to methadone treatments reduces the demand on the heroin market and thus results in a lower price for street heroin. And finally, the intensity of police activity in the drug field may also affect prices for street heroin. METHODS: As incidence of regular heroin use over more than a decade is rarely known elsewhere, we examined the Zurich experience between 1980 and 2005 by triangulating published and unpublished data, concerning heroin price, heroin purity level, heroin seizures and drug offences. This time period encompasses the time before and after the introduction of low-threshold methadone treatment in 1991. RESULTS: We found a steep peak of heroin incidence in 1990. The street price of heroin already declined from 700 to 60 Swiss Francs during the 80s. The number of heroin consumptions possession offences reported by the police increased since 1991 and peaked in 1997, 2 years after the closure of the last open drug scene. CONCLUSION: The introduction of low-threshold methadone treatment has not resulted in lower heroin prices and the increased police activity during the 90s has not led to higher heroin prices, even though the higher police activity in the late 90s may have contributed to the prevention of a re-establishment of open drug scenes. In conclusion, we did not find a close relationship between street prices of heroin, police activity, and incidence of problematic heroin use.