It has long been thought that necrotophic pathogenic fungi use a barrage of lytic enzymes to break down plant cells to access the nuritents held within. In recent years it has emerged that some necrotrophic fungi possess a more complicated and specific infection strategy, appearing reliant on a gene-for-gene mechanism as observed in biotrophic pathogens. For the wheat pathogen Parastagonospora nodorum, it has been demonstrated that the basis of this host specific interaction is small cysteine-rich effector proteins scereted during infection (ToxA, Tox1 and Tox3). It is hypothesised that these effectors interact with specific dominant susceptibility genes in the host leading to a programmed cell death response and disease. However, whilst we now understand the requirement of these effector proteins for disease, their modes of action remain poorly understood. In this seminar, I will describe the mechanisms of these effector proteins and discuss the role they play in causing disease.