The essential amino acid composition of carcasses from South African Mutton Merino ram lambs fed a standard diet was investigated. Twenty lambs were randomly allocated to four pre-assigned average slaughter weights (30, 35, 40 and 45 kg live weight). The chemical composition (moisture, fat, protein and essential amino acids of the carcass, three rib cut, M. Longissimus dorsi, M. infraspinatus flexor and M. biceps femoris was determined. The moisture and fat percentage of the three rib cut revealed the highest correlation when compared to that of the carcass. Non-significant correlations (p > 0.05) occurred between the carcass protein and the protein percentage of the three rib cut and each of the muscles. Low coefficients of determination (r2) were obtained when prediction equations for individual essential amino acid concentration in the carcass from the three rib cut or muscles remained similar regardless of slaughter weight. Isoleucine, lysine, methionine, phenylalanine and valine concentrations were significantly different (p < 0.05) either in the three rib cut or at least in one of the muscles when compared to the carcass. The carcass essential amino acid composition (5 AA / !00g protein) was as follows: 6.94 arginine; 2.61 histidine; 3.19 isoleucine; 7.19 leucine; 7.03 lysine; 2.08 methionine; 4.15 phenylalanine; 3.79 threonine and 4.28 valine. This composition can serve as an example of the ideal protein (amino acids) requirements for carcass growth of South African Mutton Merino ram lambs.