Recently, the isolation of a new class of human arachidonic acid oxidation products, the isofurans, was reported. These are produced in vivo by a free radical mechanism independent of the cyclooxygenase enzymes. Because these compounds are tetrahydrofuran derivatives that are related biosynthetically to the isoprostanes, they were termed isofurans. There are eight different isofuran regioisomers, each of which can exist as 16 racemic diastereomers. Thus, 256 enantiomerically-pure isofurans can be formed. These molecules are of interest as measurement of isofurans provides a sensitive index of free-radical induced lipid peroxidation in vivo under conditions of elevated oxygen tension. They also, in analogy to isoprostanes, may have potent biological activity. To explore this, the chemical synthesis of the IsoFs has been initiated. As a result, there is a need for a systematic nomenclature for this class of natural products. A facile system that will allow the ready differentiation of each of the isomeric structures comprising the family of isofurans is presented.