The solubility of water in n-alkanes from C6 to C-16 for temperatures from 200 to 300-degrees-C and pressures from 9.8 to 39.2 MPa was modeled using the lattice fluid (LF) theory of Sanchez and Rodgers. The theory quantitatively described the temperature, pressure, and hydrocarbon molecular weight dependence of the experimental data using a lattice fluid mixing parameter which was linearly dependent on temperature. The solubility of water in n-hexane or in n-octane along the three-phase line, which varied by over 3 orders of magnitude, could be semiquantitatively described for temperatures ranging from 38 to 265-degrees-C, when values of the mixing parameter at lower temperatures were estimated by extrapolation. The solubility of water in molten polyethylene at high temperatures and pressures was estimated based on then-alkane results. The LF model predicts that the solubility of water in low-density polyethylene at temperatures of 200-300-degrees-C and pressures of 7.0-35.0 MPa is appreciable, of the order 10(-2) kg/kg, and warrants experimental verification. This information may be useful in modeling water stripping in polymer devolatilization extrusion processes.