Across almost every county in Illinois, the majority of persons convicted of a felony that could receive probation did receive probation. The likelihood of being sentenced to prison for an offense that could receive probation exceeded 50 percent in only nine counties during the 1990's. Still, trends across individual counties in the proportion of "probational" felonies that resulted in a prison sentence varied considerably, with approximately one-third of the counties experiencing an increase, one-third having a decrease, and one-third seeing a stable trend. In addition, the proportion of prison sentences that involved "non-probationable," or Class M and X felonies, was relatively low across all counties, and stable or decreasing across most counties; however, although there was considerable variation among Illinois counties in the use of prison as a sentence when probation was an option, when prison sentences were imposed, their length, relative to the maximum that could have been imposed, was much more consistent among the counties. Conviction offense and prior criminal history had the most significant influence on the likelihood of a prison sentence; however, demographic factors, including age, gender, and race, also apparently had an influence on sentencing. 1 table