To aid future hydrogen fusion researchers, I have correlated the measured physical and chemical properties of the hydrogens below 30/sup 0/K. I have further estimated these properties for deuterium--deuterium tritide--tritium (D/sub 2/--DT--T/sub 2/) fusion fuel. My resulting synthesis offers a timely view and review of cryogenic hydrogen properties, plus some hydrogen data to room temperature. My general thrust is for workers new to the field, although my discussion of the scientific background of the material would suit specialists.