The metabolism of 1-nitropyrene (1-NP) was studied in cultured rabbit alveolar macrophages and respiratory tissues from both lung and trachea. Metabolites from the incubation medium and from the macrophages and respiratory tissues were isolated and quantitated by HPLC. The following metabolites were isolated and quantitated: 1-nitro-pyrene-4,5- or -9,10-dihydrodiol (K-DHD), N-acetyl-1-aminopyrene (NAAP), 1-aminopyrene (1-AMP), 10-hydroxy-1-nitropyrene (10-OH-1-NP), 4-,5-,6-,8- or 9-monohydroxy-1-nitropyrene (phenols), and 3-hydroxy-1-nitropyrene (3-OH-1-NP). The total percentage of 1-NP metabolism was significantly greater in the lung and tracheal tissue (28.0 to 23.0% of the recovered 14C, respectively) compared to the alveolar macrophages (6.3%). The tracheal tissue was found to have the highest activity both in 1-NP metabolism and intracellular metabolite concentration. A major portion of the 1-NP metabolites produced were released into the incubation medium.