The problem of recombination of electrons and ions in the lower ionosphere is studied both experimentally and theoretically. The experimental study involves analysis of new experimental data such as 150-kc radio wave absorption, polarization, and phase heights; absorption of short-wave galactic radiation; and E-region critical frequency, as well as recombination values already published. Then, by use of the theories of dissociative recombination and negative ions, a theoretical model is derived which is consistent with the experimental results. The values of the coefficient during night-time and during sudden ionospheric disturbances are discussed