New developments in immunological techniques and increasing expertise in genetic manipulation, especially by gene transfer, have opened up a wide variety of approaches to the manipulation of the growth and metabolism of farm livestock. However, the most effective use of these techniques and the design of new pharmacological agents for growth promotion and nutrient “repartitioning” might well rest on a greater understanding of the factors and cellular mechanisms that coordinate growth and protein anabolism. It is this coordidnation that must be disturbed if persistent gains are to bke made. This greater understanding may well result from an examination of the mechanisms whereby currently available anabolic agents and techniques exert their effects and this paper will draw on these experiences. Growth is clearly a closely coordinated process and this has hampered many attempts to maintain accelerated protein deposition for long periods. For example forced increases in hormonal concentrations often induce hormonal insensitivity. It is possible that understanding and reducing the constraints on growth for example by reducing the levels of suppressive factors rather than concentrating on the active stimulation of anabolic factors may be more effective.