Alpha-2-adrenoceptor-agonists as well as cardioselective betareceptor-antagonists have been shown to blunt stress response due to tracheal intubation. The purpose of our study was to investigate,whether clonidine or esmolol is more efficient to attenuate stress response due to intubation.44 patients were randomly assigned to receive either clonidine (n=22; 3 microg/kg) or esmolol (n=22; 2 mg/kg) immediately prior to a standardized induction of anaesthesia. Heart rate, arterial blood pressure, cardiac output, epinephrine and norepinephrine plasma concentrations were measured before,during and 10 min after intubation. Blood pressure was measured invasively and cardiac output was determined by transthoracic echocardiography. Absolute values and increase of mean arterial pressure and norepinephrine plasma concentrations were significantly less in the clonidine group (p<0,05). Clonidine (3 microg/kg) is more efficient than esmolol (2 mg/kg) in blunting stress response due to endotracheal intubation.