This chapter reviews the piecemeal development of pesticide regulation and the challenges of developing a more harmonised and global approach to approving new crop protection products. Such as approach needs to meet the needs of farmers, companies and regulators in balancing criteria such as efficacy, safety, environmental impact, cost and speed of approval. It also needs to take proper account of the distinctive features of biological products. The chapter reviews the work of the Organisation for Economic Cooperation and Development (OECD) in creating a harmonised framework to meet these objectives.