Alpha-linolenic acid, γ-linolenic acid and stearidonic acid are known to be beneficial for human health not only in their own right but also as precursors for the biosynthesis of long chain polyunsaturated fatty acids. Their utilization is, however, limited by their low levels of production, which is restricted to just a small number of agronomically poor plant species. Gao et al. (on pages 1335-1347) report on the production of these polyunsaturated C18 fatty acids in cottonseed oil, which is ranked as the sixth major vegetable oil in the world. A range of traits including oil content, fatty acid composition, nutritional value, seed germination, plant photosynthesis, fibre quality and oil oxidative stability were assessed in the transgenic cotton, thus providing vital information for potential food, pharmaceutical and industrial applications of these novel cottonseed oils.