1-Nitropyrene (1-NP), a ubiquitous environmental pollutant, is a mammalian mutagen and causes cancer in animals. The ability of the lung, liver and kidney to form 1-NP-DNA adducts was determined in adult male B6C3F1 mice following a single intratracheal instillation of 1-NP. 1-NP-DNA adducts were isolated and characterized in mouse lung, liver and kidney by HPLC analysis of the enzymatically digested DNA. Multiple DNA adducts were present in lung, liver and kidney at 1 day after administration. One of the major adducts in lung (20% of the total eluted radioactivity) coeluted with the synthetic marker, N-(deoxyguanosin-8-yl)-1-aminopyrene (C8-dG-AP). This adduct (10% of total eluted radioactivity) and others were still present in the lung at 28 days after administration of 1-NP. One of the adducts in liver and kidney DNA digests also coeluted with C8-dG-AP. Treatment of the adducts with 0.3 M NaOH resulting in earlier eluting peaks containing radioactivity, indicative of an imidazole ring-opening adduct. A portion of the original peak of radioactivity that coeluted with C8-dG-AP and other adducts, however, was not affected by 0.3 M NaOH. Thus, the chromatographic properties and chemical behavior of the adducts formed in vivo suggest that one of the adducts in the lung is C8-dG-AP which is formed by nitroreduction of 1-NP. Other adducts may be formed via ring-oxidation followed in some instances by nitroreduction. These data indicate that DNA adducts of 1-NP metabolites may be formed in the lung (a primary site for inhaled particles), liver and kidney following inhalation of airborne particles containing 1-NP.