This paper reviews the literature on taxable-income elasticities, focusing primarily on empirical studies examining the U.S. tax changes of 1981, 1986, 1990, and 1993 and the bracket creep of the late 1970s and early 1980s. The paper first provides background on the importance of the elasticity of taxable income both for forecasting income tax revenue and for assessing the efficiency implications of tax rate changes. It then discusses the major methodological issues and obstacles before delving into the literature. The paper emphasizes the different methodologies employed and the sensitivity of estimates to an array of factors, including sample selection, the tax reform under examination, and econometric techniques (or model specification). Although it recognizes advances in the literature in recent years, the paper concludes that responses to tax rate changes are far from fully understood and that there is much to be gained from continued research on this topic.