Exposure to polybrominated biphenyls (PBBs) resulted in increased activity of microsomal arylhydrocarbon hydroxylase and ethoxyresorufin‐O‐deethylase in rat lung. Clearance of 5‐hydroxytryptamine (5‐HT) and angiotensin I by perfused lungs was decreased by PBBs. However, PBBs had no effect on the activity of epoxide hydrolase, monoamine oxidase, or angiotensin‐converting enzyme in lung. The only histopathologic change detected in lungs from PBB‐treated rats was an increase in alveolar type II cell lamellar bodies. Selective accumulation of certain PBB congeners by lung was not observed in this investigation.