The effect of applied hydrostatic pressure on the enantioselective excited-state quenching of rac-tris(2,6-pyridinedicarboxylate)terbium(III) [Tb(DPA)(3)(3-)] by optically active tris(1,1-0-phenanthroline)ruthenium(II) [Ru(phen)(3)(2+)] is presented. The time dependence of the excited-state luminescence is analyzed in terms of a biexponential decay at pressures from 1 bar to 3 kbar corresponding to the diastereomeric (Delta-Delta and Delta-Lambda) quenching reactions. In water solution it is found that the diastereomeric quenching rates and enantioselectivity increase with pressure, while in methanol solution the quenching rates and enantioselectivity decrease. The results are interpreted in terms of a detailed model for the quenching involving solvation effects within the diastereomeric encounter complexes.