Complex, biologically active proteins (eg, enzymes and hormones) can be manufactured safely and cost-effectively through applications of biotechnology. Some of these proteins (eg, human insulin, human somatotropin, rennet for cheese manufacture) are currently approved for medical or food processing applications. Bovine somatotropin (bST) for lactating dairy cattle is another product that can be produced via biotechnology and may allow dairy farmers to produce milk at a lower cost. In 1985, based on an evaluation of toxicological data, the Food and Drug Administration concluded that milk and meat from bST-supplemented cows was safe and wholesome. The Food and Drug Administration has authorized the use of milk and meat from bST-supplemented cows in the commercial food supply. Its evaluation of the impact of bST supplementation on the long-term health of dairy cattle is near completion, and bST may be approved for commercial use in early 1991.