Studies have revealed systematic measurement errors in self-report data on crime and deviance resulting from poor recall and/or underreporting by certain groups of respondents. Official crime data have also been criticized, but for different reasons (e.g. gross underestimations of less serious offenses). Very similar observations have been made in studies of inmate crime (misconduct committed by prison inmates). Despite these criticisms, official data on inmate misconduct continue to be the most frequently used data in related studies. This study compared self-report and official data on inmate assaults, property thefts, and drug offenses for samples of inmates from 46 correctional institutions for adults in Ohio and Kentucky. Findings revealed that officially recorded misconduct underestimates the total volume of inmate crime. Analyses designed to uncover sources of the divergence between self-reported misconduct and officially recorded misconduct revealed far more consistencies than differences in the magnitude of inmate and facility effects on the different types of offenses. A few important differences did emerge in the magnitude of effects such as amount of time served (at the individual level) and facility population size (at the aggregate level). Abstract published by arrangement with Taylor Francis.