The prison population swelled by more than 20,000 during the first half of 1981; State and Federal correctional institutions held nearly 350,000 prisoners, compared with less than 330,000 yearend 1980. The number of Federal prisoners rose by 1,370 in the first half of 1981, with the overwhelming part of the total increase (19,000) occurring in State institutions. The largest correctional system, the Texas system, surpassed 30,000 during the report period, and 3 other State prison systems have populations of more than 20,000 -- California, Florida, and New York. Although the largest numbers of inmates have been admitted to the larger State prisons, smaller States (such as North Dakota, Utah, and Alaska) have experienced a rise in prison population. Overall, 14 States posted gains of more than 10 percent in prison population, and another 5 States had gains of close to 10 percent by midyear 1981. Four States -- Colorado, Minnesota, New Mexico, and Oregon -- decreased their prison populations during 1980 and 1981 but only by a combined decrease of 320 inmates. Record incarceration rates, particularly for female offenders, have also been reported. Items for further reading are appended; graphs and data tables are furnished.