AbstractThis chapter defines the terminologies of biodiversity, landraces, plant genetic resources, and traditional knowledge, and explores the characteristics of biodiversity and traditional knowledge, their value and the reasons for their loss, while taking into consideration both wild and domesticated plant biodiversity and associated knowledge. The relationship as well as the different patterns between the respective value and loss of biodiversity and traditional knowledge are examined. Since this is important for the design of legal instruments to regulate and protect them, the basic issues are analysed separately.