This article provides empirical estimates of the redistributive impact of U.S. personal income tax over the period [1979][1980][1981][1982][1983][1984][1985][1986][1987][1988][1989][1990]. The estimates are based on tax return data compiled from the Ernst and Young/University of Michigan tax research database. The authors employ the Gini coefficient decomposition methodology of Lambert and Aronson to distinguish between the vertical, horizontal, and reranking effects of the tax. The authors show growing pre-and posttax income inequality for the United States over the study period. But the data also suggest that the amount of horizontal inequity associated with the U.S. personal income tax is relatively low. This article also contains some international comparisons. The redistribution associated with income taxes in the United Kingdom and Spain has been measured with the same methodology the authors employ. These two countries are also characterized by growing pre-and posttax inequality, although the level of inequality is less there than in the United States. A final interesting point of comparison, however, is that the amount of horizontal inequity associated with the tax appears less than either in the United Kingdom or Spain.