Water blown, thermosetting unsaturated polyester-polyurethane hybrid foam compositions are formed by the reaction of an A side composition and a B side composition. The A side composition comprises a polyfunctional isocyanate compound and a free radical initiator. The B side composition comprises a mixture of: (i) an ethylenically unsaturated monomer solution having dissolved therein about 30-90 weight percent of a polyester polyol having at least one ethylenically unsaturated group per molecule which has predominantly hydroxyl end groups; (ii) an amine compound having two or more primary or secondary amine groups in an amount effective to react with the A side composition to form small urea domains finely dispersed within a continuous polyester-polyurethane hybrid phase; and (iii) about 25 to about 150 equivalents water based on 100 equivalents of active hydrogen in the B side. When the A and B side compositions are reacted, the composition will have a ratio of active NCO groups of the isocyanate to active NH groups of the amine compound of between about 10:1 and about 50:1. and an isocyanate index, NCO:(NH+OH+COOH+HOH), of between about 0.5 and about 2.0.