The pharmacological effects of the centrally acting antihypertensive drug guanfacine are reviewed. 2. The drug lowers systemic blood pressure in hypertensive rats dose-dependently after oral application of 0.3-5 mg/kg. 3. Evidence is presented that guanfacine produces its antihypertensive action by a specific stimulation of central alpha-adrenoceptors. 4. Certain pharmacological differences between clonidine and guanfacine are discussed.