Abstract: Thermosetting resin composition comprising an unsaturated thermosetting polyester resin and a thermosetting organo-silicone compound which can react with the thermosetting polyester resin by cross-linking to establish chemical bonds between the thermosetting polyester resin and the thermosetting organo-silicone compound for forming a solid polyester/organo-silicone thermoset resin product with a network of cross-linked chemical bonds. The thermosetting organo-silicone compound preferably is a thermosetting organo-silicone elastomer; the composition preferably contains a low-profile or low-shrinkage additive; and the polyester resin preferably is associated with an unsaturated monomer for cross-linking therewith. The resin composition is useful for the production of "dough" moulding compounds, sheet moulding compounds, bulk moulding compounds, high strength moulding compounds, and thick moulding compounds.