Drug interdiction does not emerge as a cost-effective approach to reducing drug addiction. Over a wide range of assumptions and parameter values, the results remain essentially unchanged. Interdiction rates of 50 percent, regarded as the objective, will prove largely ineffectual. Rates in excess of 90 percent and possibly higher are needed to realize significant street supply reductions. The very high cost, the large area involved, the constraints on the action law enforcement agencies can take, and the ability of smugglers to rapidly adapt to any new situation all suggest that interdiction rates of 90 percent most likely cannot be achieved and rates of even 50 percent are unlikely. Interception of laundered money or the flow of money back to the drug barons offers more promise of realizing the goal of making drugs unavailable and can be carried out at significantly less cost than that of drug interdiction efforts. 8 figures and 8 references