The haemodynamic effect of enflurane has been examined in two groups of geriatric patients, one with and the other without preanaesthetic administration of 15 mg/kg of 1,8% dextran in lactated Ringer's solution. All the patients have been immobilized for 2 to 3 days before they were operated for an orthopaedic procedure. The administration of the colloidal solution led only to minor cardiovascular alterations: a rise of central venous pressure by 6 +/- 1 (+/- S.E.M.) cm H2O, an increase of mean arterial pressure by 6 +/- 2%, an increase of cardiac output by 10 +/- 4%. Heart rate decreased by 5 +/- 4% and total peripheral resistance by 12 +/- 5%. The cardiovascular depressant effect of enflurance was markedly attenuated by the preanaesthetic volume administration. Mean arterial pressure decreased during anaesthesia by only 16 +/- 3%, as compared with a decrease of 25 +/- 7% in the control group, cardiac output remained virtually unchanged (-3 +/- 9% vs. -37 +/- 5% in the controls) and total peripheral resistance decreased not significantly by 10 +/- 12%, while it rose in the controls by 20 +/- 8%. These findings support the hypothesis that the particular sensitivity of geriatric patients towards the depressant effects of anaesthetics is at least partially due to a compensated hypovolaemia which occurs as a physiological adaptation to immbolization. Enflurane appears as a suitable anaesthetic for geriatric patients, if proper measures for preanaesthetic volume substitution are taken.