Abstract
The third paper of this series provides a theoretical basis for analysis of precision measurements of the fine structure of hydrogen and deuterium. It supplements the Bechert-Meixner treatment of a hydrogen atom by allowing for the presence of a magnetic field, as well as radiative corrections. The theory of hyperfine structure is somewhat extended. Stark effects due to motional and other electric fields are calculated. Possible radiative and nonradiative corrections to the shape and location of resonance peaks are discussed. Effects due to the finite size of the deuteron are also considered.