Traditional cultivated grapevine (Vitis vinifera) is susceptible to many fungal and oomycete pathogens causing devastating diseases including powdery mildew, downy mildew, grey mould, black rot and trunk diseases. These infections trigger various defence mechanisms such as reinforcement of the cell wall structure, production of phytoalexins and patho- genesis-related proteins, and localized cell death. In V. vinifera susceptible varieties, these defences are not effective, while in resistant grapevine, recognition of the pathogen induces effective mechanisms that stop the infection. Breeding programmes are con- ducted to take advantage of this genetic resistance. Moreover, a range of exogenous defence stimulators can be used to obtain a so-called “induced resistance” in susceptible varieties. This chapter presents the recently acquired knowledge on the molecular mechanisms involved in genetic and induced resistances, and further consider other mechanisms such as ontogenic resistance. It also suggests how to exploit these resis- tances to durably protect vineyards against the different fungal diseases.