Recent declines in both crime rates and the rate of increase in prison populations have suggested that the current prison overcrowding will be a short-term problem. However, forecasts based on present sentencing policies and the effects of recent legislation suggest that prison populations will resume their growth in most States toward the end of the 20th century or at the start of the 21st century. The forecasts focused on Arizona, California, Florida, Illinois, Massachusetts, North Carolina, Pennsylvania, and Utah. The forecasting method merged U.S. Census Bureau projections, data on the States' current imprisonment policies, and existing criminological theory on the behavior of individual offenders. The model used probabilistic concepts associated with operations research. The analysis indicated that the overall growth will be accompanied by great variations among States. Figures and 11 reference notes.