Aim of the following thesis is the clarification of the physical cause for the occurrence of tiger stripes on polypropylene moulded parts. A surface defect, which often occurs in the injection moulding technique, is characterized by a cyclic sequence of shiny and matt stripes at the flow front. Using different examination methods as well as simulation injection moulded parts are to be analyzed systematically with regard to the crucial variables influencing the occurrence of tiger stripes. The results of the microscopic examinations via laser-confocal- and stereomicroscopy showed cracks in the grains in the area of the matt spots. Within these cracks an accumulation of talcum particles was found on the surface. By means of infrared spectroscopy and upright microscopy, orientation differences within these areas of matt shininess were detected. Factorial designs, which were carried out both for the experiment and for the simulation, proved the injecting velocity to be the most relevant parameter in the occurrence of the tiger stripes. The physical cause of the occurrence of tiger stripes was identified by using a simulation of the mould filling phase of the injection moulding procedure. Caused by the re-melting of already frozen outer layers the thermally damaged material reaches the surface and leads to spots with a matter shininess in appearance. As a consequence it seems possible to predict the occurrence of tiger stripes by means of Moldflow-Simulation.