Butadiene monoepoxide, an active metabolite of 1,3-butadiene, was reacted with deoxyadenosine, deoxyadenosine 3'-monophosphate and DNA. The nucleoside reaction products were isolated and using various spectroscopic techniques were determined to be the N6-substituted deoxyadenosine adducts. Deoxyadenosine 3'-monophosphate products were identified by treating the modified nucleotide products with alkaline phosphatase, resulting in nucleoside adducts with HPLC retention times similar to those of the deoxyadenosine adducts. Monophosphate products were also identified through MS/MS techniques by comparing the daughter ions derived from the base moieties of N6-alkylated nucleosides and nucleotides. The reaction mechanism in aqueous solution was studied using optically active butadiene monoepoxides. Using the alkylated monophosphate standards and an HPLC/32P postlabeling assay the N6-alkylated adenine adducts were detected in calf thymus DNA exposed to butadiene monoepoxide.