Briefly, the four major biochemical systems respon sible for maintaining body protein and amino acid bo meostasis are 1) amino acid transport and uptake, 2) amino acid oxidation and catabolism, 3) protein syn thesis, and 4) protein breakdown. It is now quite clear that the initial response to an inadequate amino acid or nitrogen intake is a reduction in the rate of amino acid oxidation. This is followed by or simultaneously associated with a decline in the rate of specific organ and tissue protein synthesis. Protein and amino acid metabolism in both muscle and liver is profoundly af fected by a restricted dietary protein(amino acid) in take, with reduced rates of muscle protein synthesis and of the synthesis of export proteins from liver oc- curring at a relatively early period(14). These changes lead to an altered pattern of body protein distribution with skeletal muscle being affected to a greater extent than body weight or total body protein mass(13, 15) Hence, an assessment of muscle mass and/or its met abolic and functional status would be a logical focus of attention, as also would be the measure of blood proteins that are synthesized within the liver Further, the responses of organ protein metabolism to altered protein and amino acid intake are associated with and/or due to a variety of hormonal changes(16 Thus, measurement of specific hormone levels might usefully to the biochemical evaluation of protein nutritional status. It appears, however, that changes in hormones are quite variable and depend on the du