The sensitivity of adduct detection using two enhancement methods, the incorporation of butanol extraction or nuclease-P1 treatment, was determined. Phosphorus-32 postlabeling assays were conducted on lung cells from rats exposed in-vivo and in-vitro to 2- aminoanthracene (613138) (2AA), 2,4,6-trinitro-9-fluorenone (129793) (TNF), and nitrosated coal dust (NCD). Male CD-rats were dosed three times via intratracheal instillation for the in-vivo assay. For the in-vitro study, rat lungs cut into small pieces were treated with test substances for 16 hours without exogenous activation. Both the butanol and the nuclease-P1 methods detected DNA adducts caused by all three test agents. However, a higher adduct detecting ability was noted with the butanol enhancement for 2AA and TNF, and with the nuclease-P1 enhancement for NCD. The authors suggest that the butanol enhancement overall was the more sensitive protocol. However, when detecting unknown adduct forming chemicals, particularly in complex mixtures, both methods may have to be used.