It is widely accepted that the intake of n-3 polyunsaturated fatty acids (PUFAs) in the human diet should increase, in particular the long chain n-3 PUFAs such as docosahexaenoic acid (DHA, 22:6n-3). Diet has a significant effect on the fatty acid profile of lamb muscle. Meat from concentrate-fed lambs generally has the highest ratio of n-6:n-3 PUFAs, although supplementation with fish oil has been used to enrich the 22:6n-3 content of lamb (Wachira et al., 2002). Lambs finished off grass, a rich source of α-linolenic acid (18:3n-3) tend to have the lowest n6:n3 ratios. However the 18:3n-3 content of grass decreases with advancing maturity and exposure to shading (reviewed by Dewhurst et al., 2006). With a large proportion of UK lambs finished during late autumn when pasture may have a low nutritional value, the health benefits of late season lamb could be reduced. The aims of the current trial were to investigate the effects of lamb finishing system and fish oil supplementation on the fatty acid profile of sheep meat, produced during autumn and winter finishing.