Data were obtained from the statistical analysis centers of Delaware,Illinois, Iowa, Maryland, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Washington, Wisconsin, and Wyoming. The data periods for each State vary but encompass 1977-1983. The average prison stay was 1.5 to 2.5 years for all persons imprisoned for felony convictions. The time served for those convicted of violent crimes averaged 2.5 to 4 years, with the longest periods for homicide and rape. Factors affecting the time served in each State include the extent of judicial and parole discretion, the use of credit for pretrial detention time, correctional policies that shorten or lengthen time served, and jurisdictional sentencing philosophy. Factors affecting the statistical comparability of time served among the States are whether data are the mean or median times served and the distribution of the values of time served. Comparisons of time served are valid for different offenses in the same State, since the same laws and policies apply. Such comparisons universally show an inverse relationship between offense seriousness and the percentage of the sentence served. 2 data tables and 1 graph.