On an annual basis, the 1982 midyear growth is equivalent to 14.3 percent. The prison population will exceed 400,000 during the third quarter, and the 1982 increase will probably set a new high. Most of the 6-month growth occurred in the State prison population, but the Federal prison population also increased. For the Nation as a whole, the percentage increase in admissions to prison during 1981 was 5 times that of releases. Prison population increases are due to such factors as new State mandatory sentencing laws and parole release guidelines. Data are given on specific States and by region and for Federal institutions. Five tables and one graph are included.