Equilibrium vapor pressures, p, are reported for the systems tetrahydrofuran + poly(vinyl methyl ether) and tetrahydrofuran + polystyrene at 20, 40, and 60 degrees C. These data plus information from the literature serve to demonstrate that the composition dependence of p can be modeled quantitatively for polymer Solutions in thermodynamically very different solvents by means of three, physically meaningful parameters.