Tachycardia and hypertension may cause myocardial ischaemia in patients with coronary heart disease going through major surgery. Thoracic epidural analgesia (TEA) has been reported to be beneficial in this situation. The haemodynamic effects of TEA in aortocoronary bypass surgery were investigated in 30 male patients < 65 years old and with ejection fraction > 0.5. They were randomized into 3 groups: the high dose fentanyl (HF) group receiving high-dose fentanyl (55 micrograms.kg-1) anaesthesia, the HF+TEA group receiving the same fentanyl dose+TEA with 10 ml bupivacaine 5 mg.ml-1 followed by 4 ml every hour, and the low dose fentanyl (LF) + TEA group receiving low-dose fentanyl (15 micrograms.kg-1) anaesthesia+TEA. Haemodynamic parameters, the use of vasoactive and inotropic drugs and fluid balance were followed during the operation and for 20 h postoperatively. Before bypass the only significant difference between groups was a higher mean pulmonary arterial pressure in the HF+TEA group and a lower systemic vascular resistance (SVR) in the LF+TEA group, both compared to the HF group. 89% of epidural group patients needed small doses of ephedrine whereas more HF group patients were given nitroglycerine. During bypass SVR and mean arterial pressure (MAP) were significantly higher and pump flow lower in the HF group compared to the LF+TEA group. More ketanserin to HF group patients and methoxamine to epidural group patients were given. After bypass heart rate increased in all groups. Lower MAP 0.5 h after bypass and higher filling pressures in the early post bypass period in the epidural groups, most pronounced in the HF+TEA group, were noted.(ABSTRACT TRUNCATED AT 250 WORDS)