The adrenal glands of the rat do not appear to be necessary for the development of experimental renal hypertension by kidney encapsulation. Male and female rats became hypertensive when both kidneys were encapsulated with latex envelopes whether they were adrenalectomized two weeks prior to or at the time of kidney encapsulation. The type of hypertension produced in adrenalectomized rats did not differ from that of rats with intact adrenals with regard to time course of development of the elevated blood pressure (6–8 weeks), maximal elevation attained (190–220 mm Hg), polydipsia and hypertrophied hearts.