Peripheral PRA was examined in 11 patients with graft artery stenosis after the onset and throughout the course of hypertension. In the acute stage PRA was elevated in 9 patients and decreased to normal in the later stage of hypertension in all but 1 patient with malignant hypertension. The findings suggest that the determination of peripheral PRA is helpful in diagnosing graft artery stenosis only in the acute stage of hypertension, but it has no unequivocal value to the prognosis of hypertension or indication for operation.