In this paper the authors describe the results of a research programme which has investigated the links between the orientation distribution of short fibre reinforced composites produced during injection moulding and the mechanical properties of the resulting moulded components. A variety of injection moulded parts, including both model shapes (e.g., a transverse ribbed plate) and commercial products, has been manufactured and studied, both experimentally and using simulation. The fibre orientation distribution (FOD) has been characterised for each component at a number of chosen locations using an in-house developed image analyser. Measurement of the FOD for a range of different component shapes has led to the proposal of a number of preliminary design rules, which have been incorporated into a knowledge based engineering (KBE) design package. A crucial component of the KBE design optimisation is the use of a simulation package to predict the FOD for any component shape. Therefore, the accuracy of the principal commercial simulation package for FOD prediction, Moldflow, has been investigated by comparison with the experimentally measured FODs. Finally, the link between FOD and mechanical properties (both elastic modulus and fracture) has been studied by comparing analytical predictions with mechanical measurements.