Higher vertebrates can rely both on an innate as well as an adaptive immune system for defense against invading pathogens. In contrast, plants can only employ an innate immune system that largely depends on the production of antimicrobial compounds such as plant defensins and other pathogenesis-related proteins. Plant defensins are ubiquitous, cationic, cysteine-rich plant peptides and have a folding pattern that shares high similarity to defense peptides of mammals and insects, suggesting an ancient and conserved origin. A large number of plant defensins appear to display antifungal activity. Some of these defensins have been found to interact with fungal-specific components in the plasmamembrane, resulting in membrane permeabilization. This makes them an attractive source of potential therapeutics to treat fungal infections.