Abstract: A method for producing polyester modified, polyurethane foam having a density of from about 1 to 40 pounds per cubic foot, and the product produced by said method, are disclosed and claimed. A first composition or mixture is prepared comprising a relatively high molecular weight polyol, and a minor but effective amount of a hydroxy-containing, unsaturated polyester, soluble in or miscible with the polyol; a second composition or mixture is prepared comprising an isocyanate or polyisocyanate soluble in or miscible with a vinylidene type cross-linking monomer for the unsaturated polyester, the cross-linking monomer being exemplified by styrene, said first and second mixtures being blended together just prior to production of the foam, thereby enabling the production of a more homogeneous foamed product having improved physical properties, especially those enhancing the product's usefulness for insulation purposes.