Results show that all of the indexes performed fairly well. The Median Sentence Ranking (MSR) proved superior to both the National Offense Index (NOI) and the Median Statutory Maximum Ranking (MSMR) both in its ability to predict a sentence of imprisonment and to predict the principal offense. The MSMR proved superior to the NOI in its ability to predict a sentence of imprisonment, however, the NOI proved superior to the MSMR in predicting the principal offense. The MSR is the better choice when the aim is to investigate or control for the influence of offense seriousness on the likelihood of imprisonment. The MSR is also the better choice when the task is to identify which of two offenses will incur a more severe sentence. The NOI did not perform as well as the MSR in either task, however, the study showed the NOI to be a relatively robust measure of seriousness which may make it useful when alternative measures are not available or cannot be derived. For example, the NOI may provide a better measure where the aim is to predict outcomes outside the criminal justice system predicting employment prospects for ex-offenders where the offense seriousness measure should reflect employer perceptions of prior offending, rather than the courts' perceptions. 3 tables, 6 notes, 12 references, and 4 appendixes