Simple equations are derived that describe element diffusion in radiative stellar interiors and that may be incorporated in standard stellar evolution codes. For the sun, diffusion is expected to increase the predicted event rates in the Cl-37 solar neutrino experiment and in electron-neutrino scattering experiments by 5 - 10 percent; the expected increase in the predictions for Ga-71 solar neutrino experiments is between 1 and 3 percent. 38 refs.