1. The effect of vasodilatory beta-adrenoceptor blockers on regional blood flow in the major organs of anaesthetized rats was investigated using radioactive microspheres. The administration of propranolol and saline was used as a control. 2. Intravenous injections of carvedilol (2 mg/rat), celiprolol (20 mg/rat) and bopindolol (1 mg/rat) equally decreased systemic blood pressure (SBP) by approximately 20 mmHg, whereas propranolol (1 mg/rat) decreased SBP only slightly but not significantly. 3. Heart rate was significantly decreased by carvedilol, celiprolol, bopindolol and propranolol. 4. Coronary blood flow was markedly increased by carvedilol, but not by the other three drugs. 5. Cardiac output tended to decrease following the administration of all four drugs. 6. Total peripheral vascular resistance was not significantly affected by carvedilol, celiprolol and bopindolol, but was markedly increased following propranolol. 7. Renal blood flow was markedly increased by carvedilol. 8. Blood flow in the brown fat was markedly increased by carvedilol and bopindolol, but not by celiprolol and propranolol. 9. These findings indicate that the newer vasodilatory beta-blockers, such as carvedilol and bopindolol, have a beneficial effect on the regional circulation in contrast with the classical beta-blocker propranolol. 10. The regional haemodynamic effects observed in the present study following intravenous injection of the beta-blockers may help explain the clinical experience that vasodilatory beta-blockers increase insulin sensitivity and decrease mortality in patients with congestive heart failure.