The paper claims that there are too many prisoners and prisons in the United States today because sentencing policies, for most of the last half of the 20th century, have not been harsh enough; society has not been willing enough to imprison serious offenders. Research into the relationship between sentencing policy and crime control suggests that: (1) prisoners are much more powerfully deterred from criminal acts by an increase in the likelihood that the penalty will be imposed than by an increase in the severity of the penalty; (2) the quickest and least expensive way to increase the certainty of imprisonment is to change sentencing policy; and (3) sentencing to prison all offenders convicted of violent crime, without the option of probation or jail, would likely be cost-effective, may actually reduce the prison population and will eventually result in fewer arrests and convictions. Tables, notes, bibliography, appendix