The major purpose of this paper are to survey the published data on the size distribution of personal income in a number of countries belonging to the Organization for Economic Co-operation and Development (OECD), to point out the shortcomings of currently collected data, and to propose improvements. An important conclusion concerning the first purpose is that in recent years there has been no clear and unambiguous movement toward greater income equality in most countries studied. Another conclusion of this paper is that summary measures, such as the Gini coefficient, must be interpreted with great care since different summary measures of the same data may show opposing tendencies. It is clear that most countries have very poor data for policy-relevant analysis. If this situation is to be remedied, it will be necessary not only to make a much bigger effort of data collection, but to broaden the coverage of the data to correspond more closely with meaningful concepts of economic welfare. Whatever set of policies is adopted in the future will require efficient statistical monitoring to assess their impact and efficiency. At present, this cannot be said to exist in any country. The main areas for improvement revolve around the following issues: definition of income, income unit, dis-aggregation, time period of analysis, the redistributive impact of the public sector, and methods of investigation. (Author/AM)