The pressure and the compressibility of solid H2 and D, are obtained from ground-state energies calculated by means of a modified variational lowestorder constrained-variation (LOCV) method. Both fee and hcp structures are considered, but results are given for the fee structure only. The pressure and the compressibili O, are calculated or estimated from the dependence of the ground-state energy on density or molar volume, generally in a density 3 region of 0.65cr-" to 1.3o.-', corresponding to a molar volume of 12-24 cm /mole, where o.=2.958,~, and the calculations are done for five different two-body potentials. Theoretical results for the pressure are 340-460 atm for solid ~ at a particle density of 0.82o. 3 or a molar volume of 19 cm3/mole, and 370-490 atm for solid 4He at a particle densi O, of 0.92o'-3 or a molar volume of 17 cm3/mole. The corresponding experimental results are 650 and 700atm, respectively. Theoretical results for the compressibility are 210• 10 -6 to 260x I0 -6 arm -1 for solid ~ at a particle density of 0.82o "-3 or a molar volume of 19 cm3/mole, and 150xi0 -6 to 180x10 -6 atm -1 for solid D2 at a particle density of 0.92o .-3 or a molar volume of 17cm3/mole. The corresponding experimental results are 180x10 -6 and 140x10 6 arm-l, respectively. The agreement with experimental results is better for higher densities.