"Mexican drug-trafficking organizations, terrorist organizations, and other groups with malevolent intent finance their operations by moving funds into or out of the United States. For example, a common technique used for taking proceeds from drug sales in the United States to Mexico is a method known as bulk cash smuggling.1 The National Drug Intelligence Center (NDIC) has stated that proceeds from drug trafficking generated in this country are smuggled across the southwest border and it estimates that the proceeds total from $18 billion to $39 billion a year. NDIC also estimates that Canadian drug-trafficking organizations smuggle significant amounts of cash across the northern border from proceeds of drugs sold in the United States."

Source

Statement of Richard M. Stana, Director Homeland and Security Issues, Government Accountability Office, before the Senate Caucus on International Narcotics Control, "Moving Illegal Proceeds: Opportunities Exist for Strengthening the Federal Government's Efforts to Stem Cross-Border Currency Smuggling," March 9, 2011, GAO-11-407T, p. 1.
http://www.gao.gov/products/G…