Although growth in the U.S. prison population over the past twenty-five years has been widely discussed, few studies examine changes in inequality in imprisonment. We study penal inequality by estimating lifetime risks of imprisonment for black and white men at different levels of education. Combining administrative, survey, and census data, we estimate that among men born between 1965 and 1969, 3 percent of whites and 20 percent of blacks had served time in prison by their early thirties. The risks of incarceration are highly stratified by education. Among black men born during this period, 30 percent of those without college education and nearly 60 percent of high school dropouts went to prison by 1999. The novel pervasiveness of imprisonment indicates the emergence of incarceration as a new stage in the life course of young low-skill black men.