Bovine somatotropin(bST) or bovine growth hormone (bGH) is a protein of 191 amino acids produced by the anterior pituitary gland of cattle. Recombinant bovine somatotropin(rbST) is biosynthetic versions of the naturally occurring pituitary hormone in cows. The use of rbST in dairy cows promises to improve the efficiency of milk production around the world. Using recombinant DNA technology, bST can now be produced in commercial quantities. The recombinant bST(rbST) is biologically identical to the found in the bovine pituitary. Milk from rbST-treated cows has been found to have the same nutritional value and composition as milk from untreated cows. In November of 1993, rbST finally was approved by the FDA, nearly 10 years after filing a licence applica-tion. rbST has been one of the most extensively studied animal drug products to be reviewed by the agency. Three scientific facts will help to reassure the public about the safety of the milk suppy.: 1. rbST has no biological activity in humans when indigested orally or when given by intramuscular injection. 2. Insulin-like growth factor 1(IGF-1) is not orally active. Any changes in IGF-1 levels in milk are well within normal variation and are lower than those reported in human milk. 3. All cow's milk contains bST, and no significant change in bST levels in milk occurs as a result of giving cows supplemental bST. Based on the scientific evidence, the public can be confident that milk and meat from rbST-treated cows is safe to consumers.