A sense of scale is a prerequisite to thinking sensibly about illicit drug markets. For example, knowing whether a country consumes tens, hundreds, or thousands of metric tons (MTs) of a prohibited substance is critical for understanding the impact of a three-MT seizure at a border crossing. But decision-makers need more than a sense of scale; they also need figures with enough precision to be able to determine whether the markets have become larger or smaller over time. This book provides information on what America's users spend on illegal drugs and which markets have become larger. It also discusses what heroin, cocaine, methamphetamine, and marijuana are and the consequences of drug use.