A theory is presented for the plasma recombination that would have taken place when the Universe had expanded and cooled to a Primeval Fireball temperature of about 4000° K. The computed residual ionization of the hydrogen following this recombination is in the range of 2 X 1O~ to 2 X 10~, depend- ing on the assumed cosmological model. In the closed cosmological model the matter temperature would have effectively decoupled from the radiation at a temperature of 12000 K, while in the lowest density model the matter temperature would not have fallen much below the radiation temperature before the galaxies formed. Also computed is the effect of the recombination radiation on the spectrum of the Prime- val Fireball