Sprayable polyurethane compositions contain particulate filler in both polyol and isocyanate components for a total content of minimally 30 weight percent of particulate filler and fibrous reinforcement. The isocyanate component is stable with respect to storage, and composite structures prepared therefrom exhibit high modulus and can be used as replacements for unsaturated polyester systems. Resin transfer molding systems employ the same components and produce molded parts with good physical properties.