Two methods for calculating the radiation dose from remaining body activity have been suggested. One requires correction of the cumulated activities so that they reflect the activity uniformly distributed in the total body. The other method requires correction of the S values so that a value of S for the target organ from the remainder of the body is obtained. These two methods give the same answer. We have examined these methods and the number of steps required to calculate the radiation dose in each case. Our results show that the method of correcting the cumulated activities is preferred, especially if the number of source and target organs is large and a computer equipped with the necessary software is not available.