International agricultural research has historically been an example par excellence of an open source approach to biological research. Beginning in the 1950s and especially in the 1960s, a looming global food crisis led to the development of a group of international agricultural research centers with a specific mandate to foster international exchange and crop improvement relevant to many countries. This formalization of a global biological commons in genetic resources was implemented through an elaborate system of international nurseries with a breeding hub, free sharing of germplasm, collaboration in information collection, the development of human resources, and an international collaborative network. This paper traces the history of the international wheat program with particular attention to how this truly open source system operated in practice and the impacts that it had on world poverty and hunger. The paper also highlights the challenges of maintaining and evolving such a system over the long term, both in terms of financing, as well the changing ‘rules of the game’ resulting from international agreements on intellectual property rights and biodiversity. Yet the open source approach is just as relevant today, as witnessed by the recent global food crisis and looming crop diseases problem of global significance.