The key areas of biotechnology and technology are reviewed in relation to their potential application to improve the productivity of broiler chickens. Seven major aspects were identified, namely: genetic engineering of the genome; genetically-engineered hormones; peptides and bioactive agents; feed technology; cell fusion; gene probes and vaccine production. Only the first three are considered in this review. Many hormones and growth factors are known to affect the growth and development of poultry. Unlike the major responses found in growing pigs and lac-tating dairy cows, poultry growth is not markedly altered by an exogenous daily injection of growth hormone (GH), probably because of the lack of a pulsatile release pattern, similar to that which occurs endogenously. This example shows clearly why the application of the biotechnological products to broiler production must be closely linked to understanding of the underlying physiology of growth. Transgenic poultry with multiple copies of the GH gene have been produced using modified retroviri, but detailed information of the effects on growth are still lacking. The hypothalamic peptides which regulate GH secretion from the pituitary appear to be largely ineffective in promoting growth in poultry. However, certain bioactive compounds such as B-agonists are more promising. Investigations have commenced on the role of the insuline - like growth factors (IGF-I and IGF-II) in regulating poultry growth and development. Further studies on gene insertion in poultry may involve the IGF-I gene, but exogenous administration studies are still required. Another approach may be the use of hormone markers in genetic selection programmes. Consumer acceptance of poultry must always be considered. Biotechnology and growth physiology offer considerable potential to improve broiler production but their use must be balanced against consumer demand for the final product.