Since the introduction of electron beam (EB) physical vapour deposition (PVD) TBCs and their application to moving components in the hot gas stream, erosion has become a prime concern. This project has been involved in determining the erosion mechanism of EB PVD TBCs, in order to develop a computational erosion model. The unique columnar microstructure of the EB PVD TBCs precludes the use of the classical brittle erosion mechanisms. This meant that a thorough investigation into the erosion mechanism of the coatings was necessary before it would be possible to develop a model to predict material wastage. This paper looks at the erosion of EB PVD TBCs and discusses the type of damage caused by erosion as well as proposing a mechanism of erosion, It was found that in all cases the erosion of the coatings proceeds through the accumulation of damage in the form of horizontal cracks in the columns of the coating and subsequent removal of the fractured sections.