Ruminant products are considered as a major source of saturated fatty acids (SFA) in the human diet and a reduction in the intake of SFA along with a concomitant increase in the intake of n-3 series PUFA is recommended by nutritionists (Department of Health, 1994). The major fatty acid classes in beef are the saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) and beef is a nutritionally important source of the beneficial n-3 series PUFA. Experiments investigating the effects of age on lipid composition in beef muscle have, in the main, used short time periods and also been subject to confounding effects of differences in growth rate (Rule et al., 1997). This study is part of a larger investigation into the effects of breed and diet, as well as age, on muscle lipids (Warren et al., 2003). This paper will focus on the effect of age.