Injection moulding has been used to produce polymeric samples containing active pharmaceutical ingredients. Different combinations of polymers and drugs were used and surface recrystallisation of the drug was observed in some cases. Near infrared (NIR) spectroscopy has been used to investigate drug re-crystallisation from the polymeric matrix in the form of injection moulded bars. Directly after moulding, the samples were transparent, however surface recrystallisation of ibuprofen was observed to occur over a period of several days. A partial least squares NIR calibration was performed using physical mixtures of powdered crystalline drug and polymer at varying drug concentrations. This calibration was then used to quantify formation of crystalline ibuprofen on the surface of moulded bars at a range of moulding and storage conditions. Temperature and humidity during storage was found to be the most significant factor to affect recrystallization.