According to the stuff I've read, branched chain amino acids (BCAA's) are an integral part of muscle metabolism and are the first amino acids to be used during muscle protein breakdown. Whether that is true or not, I don't know. I've also heard that BCAA's were just an advertising gimmick. All in all, I think BCAA's are a necessary part of your amino acid intake. Whey protein has the highest concentration of BCAA's of any protein source.