Reinforced polyurethane/urea elastomers with a specified proportion of urea groups and a specified proportion of urethane groups are produced from an isocyanate-reactive component satisfying specified compositional requirements and an isocyanate-terminated prepolymer produced from specified materials. Two-dimensional polyurethane molded articles produced from these reinforced elastomers are characterized by improved toughness and improved shrinkage characteristics. Such molded articles are particularly useful for making automobile components.