The most widely used measure is the rate of imprisonment, a calculation based on prison and total population that produces a rate of imprisonment per 100,000 persons. However, this measure may be inadequate or inappropriate for dealing with some policy issues. The fraction in prison is a general measure of a jurisdiction's use of imprisonment that uses a specified base population or subpopulation. It can measure overall trends in punishment practices and subgroup imprisonment rates. A chance of imprisonment measure defines the probability of incarceration given membership in a specified base population. It specifies conditional probabilities of crime commission, arrest, and so forth as they contribute to imprisonment probabilities. It can be used to examine factors in cross-jurisdictional changes in imprisonment or changes over time. Prevalence measures define the proportion of people in a cohort who are imprisoned at least once during a given period. Duration measures may include those based on release cohort and provide information necessary for projecting prison populations and indicating severity of punishment. Each of these methods has advantages and limitations in its sensitivity to differences in meanings of the use of imprisonment. 2 tables and 1 figure.