This paper presents the results from the first part of a study on the influence of reprocessing and weldlines on the properties of styrene maleic anhydride (SMA) polymer. Specimens for this study were injection moulded and reprocessed up to five times. It was found that while mechanical properties such as strength and modulus in both tension and flexure tests were virtually independent of the number of reprocessing cycles, the energy to fracture decreased as a result of reprocessing. Fracture parameters such as fracture toughness and strain energy release rate also showed little variation with reprocessing; although at times a reduction in these parameters was obtained for the fifth cycle. We found that tensile strength, fracture energy and fracture toughness were all reduced substantially in the presence of the weldline. However, none of these properties showed any significant variation with the number of reprocessing cycles.