Non-radioactive, competitive immunoassay for the quantitation of cAMP in biological fluids (serum, plasma, and saliva), tissue culture media samples, or in samples containing very low concentrations of cyclic nucleotides. This kit uses a polyclonal antibody to cAMP to competitively bind cAMP or cAMP which has been covalently linked to an alkaline phosphatase molecule. The assay is performed in a 96 well plate coated with anti-rabbit IgG antibody. The colored end product, produced by the additon of substrate to the wells, is read at 405 nm on a multiwell plate reader. The intensity of the color is inversely proportional to the concentration of cAMP present in the well.