Cyclic AMP and cyclic GMP are important intracellular second messengers for many endocrine paracrine and autocrine cell regulators. In recent years, a number of reports have appeared suggesting that cyclic CMP may also be involved in intracellular regulation. Because of their general importance of contemporary biology, several companies have developed radioimmunoassays for these important hormonal second messengers. Although known to be quite specific and sensitive, RIAs have disadvantages stemming from the use of radioactivity. Indeed, the regulatory climate regarding radioactive disposal continues to make the use of RIAs in the research laboratory more and more difficult. As a consequence, there have been a number of reports of the development of non-isotopic immunoassays for measurement of cyclic nucleotides. However, none of these tests are commercially available. In the work funded by this award, we intend to develop a group of enzyme linked immunosorbent assays (ELISAs) to measure cyclic nucleotides. These test will enable researches in many disciplines to make measurements of these molecules without having to rely on radioactivity for accomplishing the task.