The solubility of small molecules and their mixtures in polyethylene is studied using a recently proposed united atom force field.(1) By comparing the simulation results with experimental data on solubility of small molecules in semicrystalline polyethylene, it is found that crystallinity can severely effect the solubility of a solute, especially if it is highly soluble in the polymer of interest. It is also observed that small molecules form aggregates within the polymer in the liquid phase.