Evidence indicates that supply-reduction measures have been successful in countering heroin trafficking and perhaps the marijuana supply, but they have not significantly reduced the cocaine supply. Federal efforts to obstruct the drug supply system include an international program to eradicate drug-related crops, interdiction of shipments crossing U.S. borders, investigations and prosecutions of high-level drug traffickers, and State and local suppression of street-level drug dealing. The supply-reduction efforts most likely to be effective must involve a coordinated portfolio of multiple measures, more resources for current efforts and improved enforcement techniques, the obstruction of trafficking connections, and evaluation of supply interdiction efforts so as to improve their cost-effectiveness. 57 references