Two groups of male and female Syrian golden hamsters, of which the trachea was severely injured by electrocoagulation, received 6 weekly intratracheal instillations of benzo[a]pyrene (BaP) + ferric oxide in saline or saline alone. Two comparable groups of hamsters were similarly treated but had an undamaged trachea. The experiment was terminated in week 82. Treatment with BaP resulted in hyper- and metaplastic lesions and tumours of the laryngeal, tracheal, bronchial and pulmonary epithelium. There was no evidence of an increased incidence of BaP-induced tumours in the injured trachea.