This study examines the mechanics of black marketing by U.S. service members to determine ways to curtail or eliminate such illegal operations, which undermine U.S. national security. Actual court-martial cases of U.S. service members prosecuted for black marketing were empirically analyzed to determine the mechanics of the illegal operations. The results indicated that U.S. service members engaged in three different types of black market operations: (1) illegal transfers of tax-free goods, (2) illegal transfers of government property, and (3) illegal currency transactions. This study suggested that black marketing by U.S. service members was difficult to curtail due to the wide variety of mechanics employed, lack of prevention assistance by foreign host nations, and ineffective U.S. controls. Consequently, U.S. prevention efforts should concentrate on eliminating the root cause of such illegal operations: trade barriers erected by the host nation against foreign imports. Existing status of forces agreements should also be rewritten to more equitably distribute the burden of prevention efforts. Finally, U.S. prevention efforts should focus on problem areas and ensure the congruence of goals and controls.