1,2-Dichloroethane-(1,2(14)C) was metabolized by rat liver microsomes to products that irreversibly bound polynucleotides. The polynucleotides were then enzymatically hydrolyzed and the products separated by HPLC equipped with an ODS or a SCX column. The products of microsome mediated binding were identified in the HPLC eluate as 1,N(6)-ethenoadenosine to polyadenylic acid, 3,N(sub 4)-ethenocytidine to polycytidylic acid, and two cyclic derivatives to polyguanylic acid. Chromatography by ODS-HPLC of the major peak from Sephadex G-25 indicated the presence of a GSH metabolite of 1,2-dichloroethane that does not contain a nucleoside. A similar hydrophilic peak was obtained from the hydrolysis products of polynucleotides from a glutathione plus cytosol incubations in which the polynucleotides instead of being added prior to the incubation were added after the incubation. The products of the glutathione plus cytosol metabolism of (14 sub c)-1,2-dichloroethane appear to be glutathione metabolites that were co-isolated with the polynucleotides rather than covalently bound adducts. In conclusion, covalently bound adducts were identified for microsome mediated binding of 1,2-dichloroethane to polynucleotides, while no evidence was obtained for glutathione plus cytosol mediated covalent binding to polynucleotides.