Food prices are a key signal about what is happening to food security, and two dimensions are important: their average level (and whether this is rising or falling in the long run) and their volatility. Food price instability slows down economic growth and the structural transformation that is the pathway out of rural poverty. The best approaches to improving food security depend on which global food price regime is likely to drive policy formation between now and 2050. The historical path of structural transformation with falling food prices, leading to a ‘world without agriculture’, is an obvious possibility. But continued financial instability, coupled with the impact of climate change, could lead to a new and uncertain path of rising real costs for food, with a reversal of structural transformation. Management of food policy, and the outlook for sustained poverty reduction, will be radically different depending on which of these global price regimes plays out.