Interlaminar fracture is recognized as an important mode of failure of composite materials and structures. In order to characterize two bismaleinimide-matrix (BMI) composites and two polyimide-matrix (PI) composites regarding their delamination behaviour, interlaminar fracture tests in mode I, mode II and mixed-mode loading conditions were carried out. The aim of this study was to examine the fracture surfaces and to find relationships between features of the fracture surface and the corresponding mechanical data. The characteristic features of failure have been pointed out and the changes of the features with variations in matrix material, testing rate and loading mode have been shown. The results of the mechanical testing can be explained by means of SEM images.