A key to securing global food security, conserving biodiversity and achieving climate change objectives as well as other concerns of international importance will be to sustain if not enhance productivity gains in agriculture. However, there are indications that productivity growth is slowing in staple food and feed crops around the world, and that the pace of investment in agricultural R&D — a primary source of the innovations that spur productivity — has slowed as well. The nature and magnitude of these shifts are spelled out in this paper. Reinvigorating agricultural research will be pivotal to turning these productivity trends around. The public sector has a key role to play, but the private sector will also contribute. However, the actions of the for-profit private sector are shaped by commercial realities that will limit their role in many, but by no means all, developing-country markets for many years to come. Thus a complementary public–private strategy will be the key to success. The private-sector roles in agricultural research are briefly described, along with the underlying economic factors at play, as a basis for informing the important policy and institutional choices and changes that will be required if the promise of increased agricultural productivity gains is to be realised in the decades ahead. The stakes are high, not least because decisions and actions taken (or not taken) now will have consequences for many years to come.