The haemodynamic changes due to cross-clamping of the abdominal aorta below the renal arteries were studied in ten patients. Anaesthesia was induced with thiopentone and maintained with fentanyl and vecuronium and inhalation of 60% nitrous oxide in oxygen. At the fifth minute, clamping increased mean arterial pressure (Pa) by 11%, systemic vascular resistance (Rsa) by 26% and decreased cardiac output (CO) by 20%. Nifedipine was administered intranasally at this time. Heart rate remained unchanged; mean pulmonary arterial and mean pulmonary wedge pressures were slightly decreased. Pa and Rsa fell to significantly lower levels between the fifth and fifteenth minutes (24 and 43% respectively). Although CO increased by 28%, this was not significant. The administration of intranasal nifedipine during anaesthesia was well tolerated. This study demonstrated that intranasal nifedipine prevented adverse haemodynamic effects of cross-clamping of the aorta below the renal arteries.