Data were collected from the 791 correctional facilities operated by the 50 States and the District of Columbia and through personal interviews with more than 12,000 State prison inmates across the Nation. Inmates of State prisons are predominantly poor young adult males with less than a high school education. Many were first incarcerated as juveniles. In 1979, blacks, who made up 12 percent of the total U.S. population, accounted for 48 percent of the prison population; whites accounted for 50 percent; and other racial groups made up 2 percent. The largest group of inmates were 18 to 29 years old and accounted for 63 percent of the population. Nearly 3 out of every 5 inmates had not completed high school. As a group, they averaged 11.2 years of schooling. In 1979, 57 percent of the State prisoners had been convicted of violent crimes, compared with 52 percent 5 years earlier. Among the violent offenders, 30 percent had committed murder, attempted murder, or manslaughter and 45 percent, robbery. Recidivists accounted for 64 percent of the inmates in 1979. Over half of the State inmates had regularly used drugs or alcohol sometime in their lives, many in the year prior to their arrest. Almost all the inmates were held in traditional, secure-confinement institutions, with 42 percent of these held under maximum-security conditions, 37 percent under medium security, 19 percent under minimum security, and 2 percent in other classifications. More than 97,000 persons were employed in State correctional facilities in 1979. One table and three footnotes are included.