Benzo[a]pyrene (BaP), a ubiquitous potent carcinogen, has been associated with the increased incidence of human bronchiogenic carcinoma in occupational and urban settings. A detailed knowledge of the rate and pattern of metabolite formation and factors affecting their formation is essential for understanding the mechanism of action of BaP in the lung. An isolated perfused New Zealand rabbit lung preparation was used to investigate the effects of a crude airborne particuiate mixture on the metabolism of BaP. [14C]BaP with and without crude air particuiate (CAP) was administered intratracheally to an isolated perfused lung (IPL) preparation after intratracheal pretreatment of the whole animal with CAP and/or BaP, or intra‐peritoneal pretreatment of the whole animal with BaP. BaP and its metabolites were extracted from perfusing blood at 6 time points up to 180 min after administration of [14C/BaP to the IPL. BaP and its metabolites were also extracted from lung tissue, washout fluid, aveolar macrophages, and trachea bronchi at the end of the perfusion at 180 min. Patterns of BaP metabolites were determined by chromatographic techniques and liquid scintillation counting.