Grapevine (Vitis vinifera) proanthocyanidins (PAs) contribute to plant defence mechanisms against biotic stress and are also involved in organoleptic properties of wine. In this chapter, we first present the particularity of grape PAs and the molecular tools available on this species. Then, we relate the recent progresses on PA biosynthesis in plants while trying to demonstrate why grape appears as a good model to fill the remaining black boxes, in particular, mechanisms involved in polymerisation and nature of the substrates for this polymerisation, transport and storage, and regulation of the biosynthesis pathway.