Summary Oilseeds, such as soybean, cottonseed, rapeseed (canola), sunflower seed and peanut, are annual plants (O’Brien et al. 2000). They are the largest source of vegetable oils even though most oil-bearing tree fruits provide the highest oil yields (e.g. olive, coconut and palm trees) (Gunstone 2002). Oilseeds are also used in animal feed because of their high protein content. Their seeds contain energy for the sprouting embryo mainly as oil, compared with cereals, which contains the energy in the form of starch (Lucas 2000). This article reviews the main types of oilseeds; their production and processing into oil. It focuses on the role of oilseeds and their by-products in human health and disease, and highlights new developments that may provide even more benefits for health in the future.