A number of theoretical and practical aspects of designing the personal income tax system are reviewed with the objective of informing policymakers of the most relevant concepts and issues when contemplating personal income tax reform. The author, after discussing some foundational issues in taxing personal income, examines the different design aspects of the personal income tax such as the tax base, rate schedule, the intergovernmental dimension, targeting consumption and addresses concerns about global capital mobility. A comparative survey of personal income tax developments in selected OECD Member countries is also presented.