Clonidine, an alpha2 agonist, was administered through a nasogastric tube for the treatment of hypertension in a head-injury patient with elevated plasma catecholamines. Haemodynamic parameters were stabilized with a reduction in sympathetic nervous activity. The plasma clonidine concentration, measured by radioimmunoassay, rapidly increased following the administration. After cessation of oral administration of clonidine, mean arterial blood pressure gradually increased. So clonidine was again administered orally and good blood pressure control was achieved and no change in consciousness level was observed. Oral clonidine was useful and effective for hypertension in this head injury patient.