Abstract: This invention relates to an improved, matured, moldable flame resistant, thermosetting polyester resin system which includes two different polyester resin compositions. One of the resins is a relatively fast reactive resin and generally contains a minor amount of isophthalic acid and a second, slower reactive system devoid of such acid. The resin system includes suitable flame retardant or flame extinguishing compounds including antimony trioxide and a halogenated organic compound. Also present are inert filler materials such as reinforcing fibers or inert, inorganic materials.