DNA adducts produced in vivo in rat lung, liver and peripheral blood lymphocytes following the i.p. administration of several synthetic benzo[a]pyrene (B[a]P) metabolites and ring-substituted derivatives have been analyzed by the nuclease P1 version of the 32P-postlabeling assay. These include 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9-, 10-, 11- and 12-hydroxy-B[a]P, (±)-B[a]P-trans-4,5-dihydrodiol, (± )- B[a]P-trans-7,8-dihydrodiol, (±)-B[a]P-trans-9,10-dihydrodiol and B[a]P-7,-dion. Among the monohydroxy derivatives, only 2-, 9- and 12-hydroxy-B[a]P produced detectable adducts. The only dlsubstituted derivative studied that produced adducts was the trans-7,8-dlhydrodiol. The resulting DNA adducts were compared to those produced in each tissue by administration of B[a]P 9-Hydroxy-B[a]P and B[a]P trns-7,8-dihydrodlol each lead to the formation of major B[a]P adducts seen in lung and liver respectively. None of the adducts derived from either 2-hydroxy-B[a]P or 12-hydroxy-B[a]P were observed following administration of B[a]P alone.