Image analysis software was used to analyse the geometry of debris formed during the erosion of low-carbon steel by impinging solid particles. Depending on the two-dimensional aspect ratio (ratio between debris height and debris width), three different debris types could be distinguished. The most frequent type observed was a platelet-type debris as suggested by the Bellman-Levy (1981) model. This wear debris shape type covered about 60% of all acquired debris. Plain micro-machining according to Finnie's (1959) suggestion played a negligible role only, but other processes, namely ploughing as suggested by Winter and Hutchings (1974), were more important. The statistically estimated mean debris size was about 14 mu m. About 92% of all wear debris had sizes smaller than the target material grain size. This result supports the figure that 'secondary' removal modes-lip or platelet, respectively, detachment from crater rims-were responsible for material removal.