[en] The Eyring-Stover theory of survival describes the observed biological phenomena of damage and repair as steady-state processes that can be expressed in the formalism of absolute reaction rate theory. The steady-state formulation, rather than that of dynamic equilibrium, is invoked since biological phenomena, in contrast with most chemical and physical phenemena, are time irreversible. The theory is appropriate for calculating life shortening that results from environmental factors such as irradiation since it does not require universality and intrinsicality as to some theories of aging. The theory gives not only midrange mortality rate values but also end-range values, which are difficult to predict empirically. The previously calculated life shortening of mice after external x-irradiation and of beagles after internal irradiation from ²³⁹Pu or ²²⁶Ra is reviewed; life shortening at low dose levels of ²²⁶Ra is presented. 21 refs., 1 tab