3. National Committee on Colorectal Cancer Screening. Recommendations for population-based colorectal cancer screening. Ottawa: Health Canada; 2002. Available: www.hc-sc.gc.ca/pphb-dgspsp

Drug supply and drug abuse The article by Evan Wood and col-leagues1 suggesting that the seizure of 100 kg of heroin made no difference to heroin abuse in Vancou-ver is interesting, but its conclusions are open to doubt and its implications are cause for concern. In Australia over the past 2 years, there has been a significant decrease in heroin overdoses (and subsequent deaths) in association with a decrease in reported abuse of heroin.2 Over the same period, law enforcement authori-ties here have had a series of major suc-cesses in intercepting shipments of heroin and arresting those responsible.2 Wood and colleagues1 admit that the Vancouver Injection Drug User Study was not designed to look at the effects of a large seizure of heroin on supply to addicts but rather was aimed at analyzing factors related to HIV in drug abusers. Hence, their article re-ports an incidental post hoc analysis. It is possible that neither the sample of drug abusers they interviewed nor the time frame in which the interviews took place was appropriate for deter-mining changes in drug abuse after a large seizure of heroin. For example, it might be that large shipments of illicit drugs are usually stored for months be-fore being distributed (to help avoid linking importation with subsequent distribution), so that the impact of a seizure on abuse would take months to appear