Abstract
The retention of 60Co by the whole body and tissues of the rat has been investigated for periods of up to 132 days following intravenous, intraperitoneal and oral administration. After the first day the retention curves for all tissues except liver can be described by power functions. Long term retention components are present in whole-body, muscle and skeleton. Radiation dose commitments to tissues of the rat, following administration of the cobalt radioisotopes, have been compared with ICRP data. A qualitative extrapolation of the present results to man indicates that, following intraperitoneal administration of 56Co and 58Co the liver will be the critical organ, but the pancreas and kidneys will be critical for 57Co and 60Co. The lower large intestine will be the critical tissue following oral administration of cobalt radioisotopes.