Structural composites comprising an isocyanurate-modified polyurea (PUrI) matrix and pre-placed mats of continuous-fibres were produced in cycle times of < 60 s via reaction injection moulding. The morphology and properties of the PUrI matrix were characterised using the SAXS, TEM, DMTA and tensile stress-strain techniques. Various hybrid SRIM composites with fibre contents up to 40% by volume were produced with single outer plies of undirectional-fibre mats of either glass, carbon or Kevlar, and different numbers of inner plies of random glass-fibre mats. At a given volume fraction, tensile property data showed the modulus and ultimate elongation, parallel to the unidirectional fibre axes, to be determined mainly by the outer plies and to vary with fibre type, whereas the tensile strength varied only slightly. All of the tensile properties perpendicular to the unidirectional fibre axes were essentially independent of the outer plies and were determined by the inner random-fibre plies and the matrix. SEN fracture data were analysed using fracture mechanics to give K I C and G I C . As expected, values of K I C and G I C parallel to the unidirectional fibre axes were greater than those perpendicular, and were greater for composites comprising outer plies of unidirectional glass rather than carbon.