The plasma cortisol and glucose responses to cholecystectomy were studied in 20 healthy patients. Ten patients received preoperative intercostal nerve blocks of the 6th to 12th nerves bilaterally using 0.5% bupivacaine with adrenaline 250 micrograms. The control group had the same quantity of adrenaline infiltrated into the intercostal space. Both groups had general anaesthesia with endotracheal intubation and controlled ventilation. In the non-blocked group, the mean cortisol concentration increased from a control value of 182.5 nmol litre-1 to a peak of 686.2 nmol litre-1 at 5.5 h after incision. In the blocked group the baseline serum cortisol concentration was 283.8 nmol litre-1 and it increased to a similar peak at 5.5 h. There were no significant differences between groups. The baseline plasma glucose concentration was also higher in the blocked group (4.45 mmol litre-1 compared with 3.94 mmol litre-1), but after a brief increase following the performance of the block decreased to only 14% above control values. The unblocked group exhibited substantial increase following the start of the surgery which continued for the duration of the study period to end at a mean of 6.48 mmol litre-1. These differences were significant (P less than 0.001). It is concluded that bilateral intercostal blocks may inhibit the glucose response to surgery, but have no effect on the cortisol response.