The microdistributions of the α-particle-emitting bone surface-seeking radionuclides 239Pu, 241Am and 233U in the mouse femoral shaft have been studied using computer-based image analysis of neutron-induced and α- particle track autoradiographs, prepared from femora of CBA/H mice which had been injected with 40 kBq kg-1 of radionuclide (as citrate solution) at times from 1 to 448 days previously. Employing dosimetric methods, radiation dose rates and cumulative radiation doses to regions of the bone marrow thought to contain hemopoietic and stromal progenitor cells susceptible to neoplastic transformation to leukemia and osteosarcomas have been calculated. It has been shown that the three radionuclides differ in their relative deposition on the bone surfaces, and that patterns of changing redistribution with time are also varied. For stromal progenitor cells, which are thought to be targets for induction of osteosarcoma and are found in proximity to the bone surfaces, cumulative doses showed the trend 239Pu > 241Am > 233U, correlating well with incidences of osteosarcoma observed in mice. Cumulative doses to the primitive hemopoietic stem cells, concentrated in the central marrow and thought to be susceptible to neoplastic transformation to myeloid leukemia, were considerably lower and also showed the trend plutonium > americium > uranium.