Equations describing the yield of scavenging reactions of the hydroxyl radical and of the hydrated electron in aqueous solutions of biological interest are presented. These equations are shown to be easy to use and they accurately predict the absolute yields of radiolytic products. Examples given include the radiolysis of aqueous solutions of glycylglycine, thymine, and DNA as functions of their concentrations. The effects of nitrous oxide and of varying concentrations of added radioprotectors are also shown. Application of the equations to other systems as well as their use in the estimation of heterogenous effects is discussed.