The vibrational, rotational, and vibrational-rotational spectra of dil. H2, D2, and HD matrix-isolated in solid Kr and Xe were calcd. at zero temp. and at pressures P = 0-570 kbar. The impurity local mode frequencies were calcd. vs. pressure. The pure vibrational and rotational-vibrational transition frequencies are strongly red shifted in the solid at P = 0 with respect to their gas-phase values, and the pure rotational transitions are weakly red shifted. The agreement with Raman and IR results is generally but not uniformly good. As the pressure is increased, the transition frequencies of all the modes in solid Xe and some in solid Kr red shift with respect to their values in the solid at P = 0. At higher pressures all modes are strongly blueshifted. The local mode frequencies strongly blueshift for all P > 0. [on SciFinder (R)]