Abstract: Australian agronomy (research and extension on land, water, soil and plant management for field crop and pasture production, performed by agronomists born and/or employed in Australia) contributes to world food security mainly by increasing productivity (yield increases per unit area or input, or per head of livestock). In the last 20 years Australian agronomy has improved world food security by underpinning increased production of field crops and livestock that theoretically could support about 30 million people per year with grain plus enough meat, edible oil and dairy products to add dietary quality and flavour. This assumes that the food is in fact eaten, and not lost postharvest or used for alternative purposes. The calculated numbers of people who could be fed involve numerous assumptions and are fraught with uncertainty. About one third of the increased production has been achieved in Australia and two thirds in developing countries, mainly in Asia. Internationally, many benefits have come from bilateral projects funded by ACIAR and/or AusAID, involving scientists from Australia and a developing country, often with links to an International Agricultural Research Centre. Australian agronomists have also contributed to food security through training activities and through leadership positions in other countries and international organisations, but these benefits are impossible to quantify. Looking ahead, inertia in the system (technical innovations still to be adopted, and projects currently in progress) suggests that this level of contribution will be maintained for another decade or so; beyond that timeframe the contribution by Australian agronomists is essentially unpredictable.