Analysis of DNA adducts demands both high sensitivity and good resolution. A high-performance liquid chromatography method for 32P-postlabeled DNA adducts (32P-HPLC) was used to investigate DNA adduct formation from 38 polycyclic hydrocarbons and biphenyls in vitro. The 32P-HPLC method proved to be useful for separation, detection and characterization of DNA adducts from most of the substances. The in vitro method used to form the DNA adducts, with calf thymus DNA, nucleotide 3'-phosphates and metabolic activation through S-9 liver homogenate, gave poor quantitative reproducibility. However, the results showed that the 32P-HPLC method was suitable for characterizing DNA adducts from many substances. From 35 of the tested substances 365 DNA and nucleotide 3'-phosphate adducts were detected and characterized concerning retention times. Of the adducts, 171 were detected in DNA and 39 of them from five substances were characterized concerning target nucleotides. The retention time library built can be used in future analyses of DNA with complex patterns of DNA adducts.