This paper presents new evidence on the level and distribution of income and payroll tax burdens for U.S. families over the 1979-1999 period. During this period, payroll taxes have become an increasingly important component of the tax burden for many low- and middle-income families. This paper uses a new and expanded version of the NBER TAXSIM program to analyze the impact of legislative changes in income and payroll taxes. Averaged over all families, the combined 1999 payroll and income tax burden was quite similar to what it would have been if the 1979 income and payroll tax laws had remained in force for the last two decades, with only inflation-based adjustments to tax brackets. The mix of income and payroll taxes has changed, however. As a result of the expansion of the Earned Income Tax Credit in the late 1980s and early 1990s, as well as other changes in the federal personal income tax, payroll tax liabilities now exceed income tax liabilities for nearly two thirds of families. In 1979, payroll taxes exceeded income taxes for 44 percent of families.