cAMP is a ubiquitous cellular second messenger that is a critical component of a signal transduction pathway linking membrane receptors and their ligands to the activation of internal cellular enzymatic activity and gene expression. cAMP is synthesized from ATP by membrane-bound adenylate cyclase and activates or inhibits various enzymes or cascade of enzymes by promoting their phosphorylation or dephosphorylation. Cayman's cAMP assay is a competitive EIA that permits cAMP measurements within the standard curve range of 0.08-10 pmol/ml, typically with a limit of quantification of 0.1 pmol/ml (80% B/B0) for acetylated cAMP. Non-acetylated cAMP can be assayed with an IC50 value (50% B/B0) of approximately 20 pmol/ml and a detection limit (80% B/B0) of 3 pmol/ml.