Results show that the Federal prison population exceeds 218,000, a tenfold increase since 1980. This massive growth is projected to continue and is accompanied by increasing costs, which account for 25 percent of the Department of Justice's budget and edge out other important public safety priorities. Topics discussed in this report include: the impact of the rapid growth of the Federal prison populations; the projected population growth; the high cost of the increasing number of incarcerations; the opportunity costs that are created by growth; how the main drivers of this phenomenon are front-end decisions about who goes to prisons and for how long; how drug offenders make up half of the Federal prison population; how supervision violations make up at least 15 percent of annual admissions; how front- end changes can most directly contain future growth; how back-end changes can help alleviate the growing pressure on the system; how the Federal system can learn from the States; and recommendations for moving forward. 4 figures and 22 notes