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1. Baroreflex sensitivity was evaluated in 22 non-dialysed patients with chronic renal failure secondary to chronic glomerulonephritis. Baroreflex sensitivity was judged by the slope of the linear regression of the pulse interval on the rise in systolic blood pressure with injection of phenylephrine or reduction by amyl nitrite inhalation. 2. Baroreflex sensitivity was reduced in these patients as compared with normal controls. Reduction of baroreflex sensitivity was significantly greater in nine hypertensive than 13 normotensive patients with chronic renal failure. 3. A significant positive correlation was found between baroreflex sensitivity and motor nerve conduction velocity measured on ulnar nerve in 13 patients examined. 4. Saline was given with high dietary salt intake to seven normotensive patients with chronic renal failure for 2 or 5 days in order to determine whether the severe depression of baroreflex sensitivity can be an initiating factor for hypertension. Blood pressure was raised to hypertensive levels within 5 days in two patients in whom baroreflex sensitivity was nearly as low as that of hypertensive patients, but not in five cases whose baroreflex sensitivity was normal or only mildly depressed. Plasma volume increased to the same degree in both groups. Baroreflex sensitivity did not change in the former two cases despite blood pressure elevation. 5. It is concluded that reduced baroreflex sensitivity in chronic renal failure correlated with the presence of hypertension, as well as uraemic neuropathy, and may be one of the pathogenetic mechanisms of hypertension in end-stage chronic glomerulonephritis.