For the spatial comparison, victimization data from 26 cities surveyed by the LEAA were compared with FBI Uniform Crime Report data on offenses known to the police for those same cities. For the temporal comparison, victimization data from the annual National Crime Survey were compared with national data from FBI Uniform Crime Report data on offenses known to the police. Victimization data were transformed when necessary to crimes per capita, rather than crimes per household to make them more comparable to official statistics. For selected offenses, rates of victimization involving injury, substantial property loss, or invasion of an individual's home (serious victimizations) were compared separately to official statistics. Based on the spatial and temporal comparisons, victimization and official statistics appear to have been measuring two different phenomena: none of the offenses can be regarded as equivalent with respect to victimization and official data over both space and time. (Author abstract)