Under an association contract linking the Co ission of the European Communities and the Gesellschaft fUr Strahlen- und Umweltforschung mbH, a research programme on the patho- genesis of somatic radiation damage has been under way for a number of years. Experimental research on long-term radiation effects following the incorporation of bone-seeking radionuclides and an epidemiological study of the conse- quences for patients treated with 224Ra for therapeutical reasons have been among the main features of the work. The research carried out on tumor induction in the low dose range and for low dose rates is particularly important as regards assessing the radiation hazard to man. The second Symposium on the biological effects of 224Ra, held at Neuherberg, provided a welcome opportunity to take stock of what has been achieved so far and to discuss the own research efforts in an international setting. The dis- cussions focussed on two topical aspects of radiation protection. One aspect was the long-term effects of high-LET ionizing radiations on man and the quantitative data involved in risk assessment at low doses. The epidemiological studies and experimental research carried out under the association contract should provide facts and figures for an objective assessment of the radiation hazards from incorporated radio- nuclides, which is one of the fundamental and controversial problems of the nuclear energy debate.