With the globalization of the world's economies, the elimination of barriers to mobility within trade blocks, and the growth of consolidated multinational businesses, the movement of employees and independent contractors is an obvious feature of modern commercial life. While labour mobility may not yet be as free as capital mobility, the ground is closing. A logical response to the increased mobility of labour would be a gradual convergence of different countries' tax rules applying to expatriates, as nations seek to grapple with the same problem, and a growing harmonization of rules to prevent overlaps and double taxation while closing the lacunae which allow taxpayers to escape taxation completely.As the papers in this volume show, however, the legislatures responsible for drafting tax laws and the tax authorities responsible for administering them are many steps behind commercial developments. Indeed, if anything, the gap is widening--different, sometimes dramatically different, approaches between jurisdictions are revealed. It is, therefore, to be hoped that governments turn their attention to the problems raised in this volume and explore appropriate paths for unilateral or multilateral resolution of these issues.