Two young male patients with neurofibromatosis were found to have intrinsic abnormalities of the renal arteries which produced renovascular hypertension. The vascular lesions in both patients appeared to consist of dysplastic lesions of the arterial wall rather than compression or involvement of the renal artery with neurofibromata. One patient demonstrated vascular lesions involving three major renal arteries. In addition, intimal proliferation and fibromuscular changes in the media were observed in the small arteries of the renal parenchyma. Surgical correction of the main renal artery lesions in this case produced a poor antihypertension response, while correction of the arterial stenosis in the patient without small vessel involvement invoked a hypertensive cure. Hypertension associated with neurofibromatosis may be produced by a variety of vascular lesions among which are dysplastic abnormalities of the large and small renal arteries.