We examined road traffic crash (RTC) fatality rate data for the year 2002 with the object of determining which data source offered the most reliable estimates for international comparison work. Data from the World Health Organisation (WHO) (supplied by national health authorities) and the International Road Federation (IRF) (supplied by national transport authorities) was compared. There were large discrepancies between the rates reported. Discrepancies may be partially explained by the under-reporting of fatalities and by different definitions of road fatality. Two methodologies to adjust for these factors in the IRF database were examined. Neither brought consensus with the WHO RTC fatality rate for all nations. While the WHO provide RTC fatality rates for a wider socio-economic and geographical range of nations than the IRF, the methodology used by the WHO to produce estimates for the least economically developed nations may lead to over-estimation of RTC fatality rate. WHO RTC fatality rates were more strongly associated with variables that are thought to explain RTC fatality rate. We suggest that WHO data may be more suitable than the IRF data for international comparison studies. However, it is advisable that data for the least developed nations be excluded from such work.