The mean square angular and lateral spreads in showers have been evaluated for electrons as well as photons as functions of their energy. Analytical expressions have been obtained for high and medium energies down to the critical shower energy. The calculations have been extended by numerical methods for air down to low energies (\ensuremath{\sim}4 Mev). Radiative effects and ionization losses have been taken into account simultaneously for all energies, and we believe that no factors of physical significance have been omitted.