Abstract: 3'-Phosphoadenosine 5'-phosphosulfate, also known as PAPS, is useful in establishing sulfate transfer mechanisms in animals and may be produced by a chemical process yielding 68-72% product from a pure adenosine 2',3'-cyclic phosphate 5'-phosphate, which compound is initially prepared from the reaction of adenosine and pyrophosphoryl chloride. In the present procedure the pure cyclic phosphate is reacted with triethylamine-N-sulfonic acid to produce 2',3'-cyclic phosphate 5'-phosphosulfate. Subsequently, by hydrolysis with the enzyme ribonuclease-T.sub.2, the desired compound is produced. Alternatively, the 2'-phosphoadenosine 5'-phosphosulfate, known as iso-PAPS, may be produced from 2',3'-cyclic phosphate 5'-phosphosulfate by treatment with a different enzyme, PDase or spleen phosphodiesterase. This latter compound, iso-PAPS, biologically has only one-third the activity of PAPS, the natural isomer.