The next Gordon Conference on Cyclic Nucleotides (June 11-15, 1984) will focus on the regulation of growth and differentiation. This area is viewed as an emerging center of research activity. It has been known for many years that cyclic nucleotides affect the amount of certain enzymes such as phosphoenolpyruvate carboxykinase and ornithine decarboxylase. These nucleotides are also known to induce differentiation as in the case of slime mold aggregation, and to arrest growth in certain situations. The mechanisms for these effects have remained obscure. With the realization that protein phosphorylation plays a key role in many effects of cyclic nucleotides and with the new methodologies brought about by recombinant DNA technology, several breakthroughs are being made. The effects of cyclic nucleotides and calcium on growth and differentiation; the role of protein phosphorylation and other mechanisms in these effects; and a comparison of mammalian systems with those of simpler organisms will be examined. It will also be necessary to consider the fundamental mechanisms of the enzymes involved in the regulatory cascade systems. The subject of growth and differentiation will be approached with the knowledge that many of the enzymes of the cyclic nucleotide pathways are homologous. This knowledge not only serves as an organizational tool for the conference, but suggests experiments and directions for investigations in the cyclic nucleotide field. The approach and the general focus of the meeting have not been used before in this conference series.