The three homicide data sources are the National Homicide Monitoring Program (NHMP) at the Australian Institute of Criminology, the Recorded Crime Australia (RC), and Causes of Death (COD); the latter two collections are managed by the Australian Bureau of Statistics. Both RC and NHMP data are derived from police offense reports, and COD data are compiled from information extracted from death certificates provided by State and Territory registrars of births, deaths, and marriages. NHMP data are recorded by fiscal year; and RC and COD data are recorded by calendar year. The different recording periods prevent direct comparisons. The years that data are available for analysis also vary among the data sources. RC began collecting data in 1993, and COD data are available back to 1915. In the current study, the main comparisons between data sources are between RC and COD for the years 1993 to 2001. Comparisons were made on the number of homicides for total persons, homicide rate per 100,000 population, and absolute and percentage difference between the number and rates derived from the various data sources. Given that NHMP data are collected by fiscal year, these data were used in the examination of homicide trends over time. For the purposes of this study, homicide included murder and manslaughter but excluded traffic deaths. In accordance with results from Canadian research, the current research found that RC data consistently resulted in higher counts of homicide than COD data. Differences in homicide counts from the various data sources were minimal (an average of 9.4 percent), suggesting that the differences have little impact on the overall quantification of homicide in Australia (counts and rates); however, the findings give some concern about the reliable measurement of homicide trends, with COD and RC data yielding somewhat different conclusions regarding homicide trends. 2 tables, 3 figures, 3 notes, and 13 references