Polyurethanes are produced using a diisocyanat-polyaddition-technique. The formula containing isocyanates, polyols and catalysers defines the properties of these foams and is extremely important for further proceedings. Therefore the adequate catalytic influence is significant as far as the gelling and the blowing reaction are concerned. These reactions often proceed simultaneously. The activity and the selectivity of the used catalysers were first analysed in individual experiments and then in combined experiments, so called synergy-experiments. Therefore an ultrasonic sensor and a pressure sensor were used. As a result of these examinations five different catalysercombinations were chosen for further experiments. The effects of the catalysers on the structure of the polyurethane foams were examined with microscopic pore scans, DSC and DMA. The influence on the material properties were checked by testing the stiffness, the Youngs modulus, as well as the compression set, the tensile strength and the elongation at break. The examinations using the ultrasonic sensor and the pressure sensor have been proved to be useful for quality assurance. The effects of the used catalysers on the structure and the material properties are to be categorised as negligible in the laboratory assays.