Abstract: This study examined the impact of substance abuse on Canadian society. It estimated that impact in terms of death, illness and economic costs caused in whole or in part by the abuse of tobacco, alcohol and illegal drugs for the year 2002. In economic terms, abuse occurs when substance use imposes costs on society that exceed the costs to the user of obtaining the substance. These costs are designated as “social” costs. It is important to note that estimating social costs is not a simple accounting exercise. We do not look at actual dollars spent or at a literal body count in cases where death results in a cost to society. Rather, cost studies are based on well-documented economic theories and assumptions. For this study, in all cases where we could have used different assumptions to estimate costs, we routinely adopted the most conservative approach. Measured in terms of the burden on services such as health care and law enforcement, and the loss of productivity in the workplace or at home resulting from premature death and disability, the overall social cost of substance abuse in Canada in 2002 was estimated to be $39.8 billion. This estimate is broken down into four major categories in Figure 1. This overall estimate represents a cost of $1,267 to every man, woman and child in Canada, as indicated according to substance in Figure 2. Tobacco accounted for about $17 billion or 42.7% of that total estimate, alcohol accounted for about $14.6 billion (36.6%) and illegal drugs for about $8.2 billion (20.7%) (see Table 2). Productivity losses amounted to $24.3 billion or 61% of the total, while health care costs were $8.8 billion (22.1%). The third highest contributor to total substance-related costs was law enforcement with a cost of $5.4 billion or 13.6% of the total.