A theory of multicomponent liquid hydrogen solutions is presented which corrects for nonidealities in vapor-liquid equilibria. The second virial coefficient is used to represent gas nonideality, and a binary interaction parameter is used for liquid nonideality. The latter is the primary contribution for the deviation from Raoult's Law of H2-D2 solutions between 15 and 27 K. Estimates are made for the parameters needed to describe the D2-DT-T2 solutions of hydrogen fusion interest.