Hypertension occurring in patients with adult polycystic kidney disease (PKD) without substantially decreased glomerular filtration rate (GFRs) has not been sufficiently evaluated. Seven patients with bilateral PKD and serum creatinine clearances greater than 70 ml/min were studied to examine the roles of sodium retention and the renin-angiotensin system in their hypertension. These individuals demonstrated evidence of volume expansion and sodium-dependent hypertension. However, the renin-angiotensin system was not consistently depressed as a consequence, and two of the seven had significantly increased plasma renin activity values. It seems that patients with PKD who had normal GFRs retain rather than waste sodium and may become hypertensive. The contribution of the renin-angiotensin system is variable and seems to be a function of such factors as symmetry of the cystic involvement and the degree of intravascular volume expansion.