Plants have evolved a plethora of defence mechanisms to protect themselves against attempted invasion from pathogens and parasites. Plant resistance is the typical outcome of these interactions, while susceptibility to infection is the exception. Nevertheless, plant diseases are still widespread, resulting in blights, wilts, rots, powdery and downy mildews and rusts. In the artificial setting of agriculture, where plants are maintained as monocultures, diseases can cause severe crop loses. We are employing functional genomics based approaches, forward and reverse genetics, luciferase imaging, 3-D confocal microscopy and targeted proteomics approaches to dissect the signalling mechanisms underlying the activation of inducible plant defence responses against pathogens and parasites. New knowledge and understanding emerging from these studies will provide novel insights into rationale crop design.