We measured and compared the anaesthetic requirements, incidences of chest wall rigidity and intraoperative hypertension, and time for recovery from anaesthesia after high dose fentanyl-oxygen anaesthesia in patients with and without histories of smoking, alcoholic intake and caffeine consumption who were undergoing coronary artery bypass grafting operations. Patients without a history of smoking and alcohol or caffeine intake required less fentanyl for induction and maintenance of anaesthesia and experienced less chest wall rigidity and hypertension than similar patients who had been chronically exposed to and/or consumed these agents. Pretreatment with more pancuronium (1.5 vs 1.0 mg/70 kg) prior to anaesthetic induction and increased fentanyl (3 X vs 1 X the "sleep" dose) administered after anaesthetic induction but before incision reduced the incidences of chest wall rigidity and intraoperative hypertension in patients with positive histories of exposure to the agents to values similar to patients without histories of exposure. Our findings suggest that population habits may affect the incidence of undesirable side effects during high dose fentanyl anaesthesia but that modifications in anaesthetic technique can minimize or eliminate these problems.