This paper reviews evidence relating to the abundance of water on early Mars and Venus from measurements of the present abundance of hydrogen compounds, deuterium to hydrogen (D/H) ratios and escape fluxes. For Mars, recent measurements of D/H ratios in SNC hydrous minerals provide data on the ratios at earlier times to augment present atmospheric values. Interpretation of these data shows that they are consistent with the presence of scores to hundreds of meters of liquid water on early Mars. In that case, they also require concentrations of hydrogen compounds in the early atmosphere orders of magnitude higher than at present. For Venus, a very large D/H enhancement (160 fold) implies at least 3 to 4 meters liquid equivalent of early water (depending on how much hydrogen is in the atmosphere today). It is consistent with much more, even the equivalent of a full terrestrial ocean. The low escape flux and high fractionation factor place severe constraints on volcanic or cometary sources. Some of the present water can have been injected by volcanism but comets as important sources appear to be excluded.