The mortality from leukaemia and other cancers in the National Registry for Radiation Workers is analysed to determine the subcategories of leukaemia in which the trend with dose is most marked. Differences between external (SMR) and internal analyses (of trends with external radiation dose) are assessed for the various leukaemia subtypes. The significance of the trend for leukaemia mortality observed in the previous analysis is largely accounted for by the group of chronic myeloid leukaemias. Sensitivity analyses are performed relating to various uncertain parameters to examine the robustness of the previously published findings. The magnitude (and significance) of the trend with dose for leukaemia is robust to a reasonable range of assumptions concerning the lag period; if a lag of 5 years is used the trend retains borderline levels of statistical significance (p=0.07); if lags of 0 or 2 years are employed rather more significant trends are apparent (p=0.03).