Lesions of the anteroventral third ventricle (AV3V), an angiotensin and osmosensitive region of the anterior hypothalamus, prevent or abort hypertension in a number of rat models. To determine if A V3V lesions alter hypertension in spontaneously hypertensive rats (SHR), lesions and control sham lesions were made in young SHR at 28 days of age. AV3V lesions had no effect on the development of hypertension in SHR. However, lesioned rats demonstrated significantly reduced pressor responses to intracerebroventricular injections of angiotensin II (AH) and hypertonic NaCl, and drinking produced by centrally administered AH. The depressor effect of central AH receptor blockade was also significantly attenuated in lesioned SHR. These effects appeared to be of central origin since the lesion did not affect the pressor action of intravenous AH or norepinephrine (NE). It is concluded that unlike other models of experimental hypertension (steroid-salt, oneand two-kidney renal, neurogenic) the development of hypertension in SHR does not depend upon the integrity of the AV3V region. (Hypertension 4: 387–393, 1982)