Theoretical calculatins of electron mobility in the indirect crystals, Ge, Si, and GaP are presented. The model assumes parabolic and spherical conduction band minima and includes piezoelectric, acoustic, polar, Coulomb, and invervalley scattering with appropriate electron-phonon selection rules in all cases. Fermi statistics are accounted for and no further approximations are made, since drift mobility is calculated form an exact iterated solution.