Percutaneous transluminal angioplasty (PTA) was attempted on 16 nonatherosclerotic lesions in 14 patients. Dilatation was initially successful in 4/4 cases with renal artery stenosis due to fibromuscular dysplasia (three) and Takayasu arteritis (one); all patients became normotensive and remain normotensive on no antihypertensive medications, at up to 12 months follow-up. PTA was technically successful in 4/5 transplant renal artery stenosis; these four patients remain normotensive or almost normotensive on no or markedly reduced antihypertensive medications, at up to 14 months follow-up. Initial success was obtained in 3/3 lesions involving vascular grafts; in one, the patient became and remained asymptomatic for the remaining 5 months he lived; in another, occlusion of the dilated segment and the graft occurred 8 months after PTA; and in the third, symptoms and signs of limb ischemia returned within 24 hr of PTA. PTA was initially successful in a patient with recurrent celiac artery stenosis after surgery for median arcuate ligament syndrome; she has remained free of symptoms for 18 months. In a patient with three radiation-induced stenoses, PTA was initially successful; this patient is asymptomatic at 20 months follow-up. The medial type of fibromuscular dysplasia dilates most easily, suggesting a concentric stretching and some shearing of the fibrous tissue, which then heals in its dilated state. Intimal fibroplasia may be eccentric, and concentric stretching during dilatation may not be possible, leading to less satisfactory results. Radiation-induced stenosis involves periarterial fibrosis and arterial wall thickening, and the results in PTA of many of these lesions may be less satisfactory than reported here. The responsiveness of graft stenoses will vary with the cause; anastomotic stenoses will probably dilate easily, for they involve either concentric intimal proliferation, or a small degree of periarterial fibrosis; graft stenoses surrounded by dense fibrous tissue may respond initially to PTA, but the long-term results will probably be poor due to recurrent graft constriction.