The Annual Beltsville Symposium provides a forum for interaction among scientists involved in research that is vitally important to agri- culture and to the agricultural sciences. The Twelfth Symposium in this series focused on the unifying biochemical and physiological mechan- isms controlling growth and development of biological systems - ani- mals, plants insects. Unraveling the complex biochemical mechanisms associated with the sequencing of organism growth and development and identifying, locating, and manipulating key control mechanisms are essential in utilizing the full potential of biotechlogy for improving the composition and quality of agricultural products and the profitability of agriculture. Accordingly, speakers directed their remarks to basic aspects of biological mechanisms in their area of specialization with considera- tion given to current status, future direction, potential impact, and limitations to progress. The Symposium addressed fundamental questions in: -Tissue specific gene regulation: cell division and differentiation -Mechanisms for regulating hormone concentration -Hormonal regulation of growth and development -Non-hormonal regulation of growth and development -Nutritional regulation of growth and development Because the backgrounds of the symposium attendees covered a wide spectrum in the basic biological and physical sciences, each topic was introduced by a brief overview, but general reviews were avoided in favor of findings from on-going research projects. The symposium brought together a distinguished group of invited scientists from around the world who are leaders. Many attendees made poster presentations which increased the exchange of ideas and sti- mulated informal discussion.