Currently violent criminals are serving 37 percent of the sentence imposed. If required to serve at least 85 percent of their imposed sentences under truth-in-sentencing policy, violent criminals would serve 2.3 times longer than they do now. If the 55 percent of the estimated 800,000 current State and Federal inmates who are violent offenders served 85 percent of their sentences, and assuming that those violent offenders would have committed 10 violent crimes a year while on the street, then the number of crimes prevented each year by truth-in-sentencing would be 4,400,000. Truth-in-sentencing laws would require State prison officials to retain more inmates for longer periods, thus increasing State costs, but research shows that such offenders are generally society's most dangerous predators. The costs saved are those associated with the crimes that would have been committed had the offender not been incapacitated by incarceration. This article concludes by countering two objections to truth-in-sentencing laws: truth in sentencing would obstruct programs that provide alternatives to incarceration; and truth-in-sentencing discriminates against minorities. 3 tables and 45 footnotes