The last half of the 20th-century has seen a phenomenal increase in the volume and complexity of international business. Global economy allows multinationals to design their operations in a manner that may significantly reduce their taxes, particularly by taking advantage of tax incentives offered by many countries to attract geographically-mobile capital and activities. Since 1962, 19 countries have enacted specific statutory regimes to counteract the perceived abuse of controlled foreign companies located in tax havens. In three cases to date, controlled foreign company (CFC) legislation has been challenged in legal proceedings on the basis that it contravened a tax treaty. The author presents an in-depth analysis of the potential conflict between CFC legislation and tax treaties. The author also evaluates the potential conflict between the CFC legislation found in European Union countries and the EC Treaty. This comprehensive work should be of interest to international tax advisers.