A comparison is made of the formalisms which have been proposed to characterise the response of normal connective tissue to levels of radiation which may lead to end points other than tissue tolerance; namely, Partial Tolerance, Time-Dose-Fractionation factor, and the Cumulative Radiation Effect. It is shown that, in most situations, conclusions which may be drawn using any one formalism are essentially the same as those which follow from the use of any other.