of life-span-shortening and incidence of neoplasms. When plotted against dose, life-span-shortening and bone sarcoma induction were not linear over the whole dose range observed. Life-span-shortening and tumour induction appeared to be equally sensitive indicators of radiation damage. There was a good corres- pondence between life-shortening and tumour induction up to a dose of 880 yCi/kg but at still higher doses, in spite of a decreased incidence of the bone tumours, life-span further decreased, showing the beginning of a specific nontumorous mechanism of death. 129. Finkel's [F5] data were reanalised by Mays and Lloyd [M11]. Mice dying with bone sarcoma had a median life-span from injection to death which decreased rather regularly with increasing average skeletal dose, owing to a shorter latency time of the bone sarcoma incidence at higher doses. 1life-shortening induced by single injections of An effect of 995, (1.0 or 0.2 pCi/g) was also described by Van Putten and De Vries [V2] on (CBAxC57BL)F1 hybrid female mice and these data plotted as the percentage of the control life-span were rather close to those of Finkel et al. 130. [F5]. Similar observations can be made regarding the rat data of Moskalev, Streltsova and Buldakov [M16] as reanalysed by Mays and Lloyd [M11], since the average time from injection to death tended to lengthen as the dose decreased from 500 to 0.005 pCi/kg. Brooks et al. A dose-related life-span-shortening was reported by [B12] in hamster injected with 90.5 (0.2 to 5.0 pCi). The 60 per cent survival times ranged from 90 days with 2.0 uCi/g to 1100 days at 0.2 uCi/g. In this species, however, myeloproliferative diseases rather than os- teosarcoma were the most common pathological conditions observed. 131. Another volume seeker, Ce, was studied in single injections by Finkel et al. [F5], and her data were also reanalysed by Mays and Lloyd [M11]. They were able to show that median survival time from injection to death in mice dying with bone sarcoma declined with increasing dose owing to a progressively early appearance of the bone tumours. 132. Sarcoma incidence in the bone tissue and life-span-shortening were eva- luated as a function of dose, dose rate and time in beagle dogs fed from mid gestation to 1.5 years of age a diet containing 900 [M17]. Under these con- ditions the observed life-span-shortening was attributed mostly to radiationinduced tumours. Also, in the same paper a reduction of the delay time in the i