This version of What America’s Users Spend on Illegal Drugs (WAUSID) provides estimates of three aspects of the illegal drug world: prevalence of drug use, expenditures on drugs, and consumption of drugs. It provides prevalence estimates of the number of chronic and occasional users for each of the four major illegal drugs (cocaine, heroin, marijuana and methamphetamine) from 2000 through 2006. Based on those prevalence estimates and drug users’ self-reports of drug market behaviors, this study provides estimates of what Americans spent on each of the four major illegal drugs.