This study examined whether seizures of heroin, cocaine or amphetamine type substances (ATS) or supplier arrests for heroin, cocaine or ATS trafficking have any effect on the emergency department (ED) admissions related to or arrests for use and possession of these drugs. A time series analysis was conducted of the relationship between seizures, supplier arrests, ED admissions and use/possession arrests. There was also an analysis of three specific operations that may have affected the market for cocaine. Over the short term (i.e. up to four months), increases in the intensity of high-level drug law enforcement did not appear to have any suppression effect on ED admissions relating to ATS, cocaine and heroin, or on arrests for use and/or possession of these drugs. The three major operations dealing with cocaine did exert a suppression effect on arrests for use and possession of cocaine. (Abstract, edited)