Many protein and amino acid supplements are touted as being able to maximize the gains achieved from resistance exercise by preventing muscle protein catabolism and stimulating anabolism. If effective, such supplements would be useful not only for athletes and for those trying to increase their fat free mass, but also for patients recovering from injuries or burns and for the prevention of aging-associated muscle loss. It has been shown that intravenous infusion or oral administration of complete mixtures of amino acids has a positive effect on muscle protein synthesis and net muscle anabolism following exercise. Since nonessential amino acids are synthesized by the body in response to resistance exercise, administration of essential amino acids only following exercise has the same positive anabolic effect on muscle as complete amino acid supplementation. Furthermore, oral administration of whole proteins following training has a similar anabolic effect, as whole proteins such as whey and casein are also effective sources of essential amino acids. In addition to mixed amino acid and whole protein supplements, a number of single amino acids are marketed as having anti-catabolic and/or anabolic effects on muscle protein, including glutamine, asparagine, ornithine, and beta-hydroxy-beta-methylbutyrate (HMB). Among these, only HMB has been shown to have positive effects on gains in muscle strength and fat free mass versus placebo in combination with a program of resistance exercise. In summary, supplementation with essential amino acids, whole proteins, and HMB in conjunction with resistance training can maximize the gains of exercise alone.