Objective To undertake animal experimentation and clinical study on the safety and efficacy of percutaneous transluminal angioplasty (PTA) and intraarterial papaverine (IAP) infusion for treatment of refractory symptomatic cerebral vasospasm (CVS). Methods In the experimental study, vasospasm was induced in rabbits by double injections of blood into the cisterna magna, IAP infusion was given on either the 4th day or the 7th day after occurrence of subarachnoid hemorrhage (SAH), and then neurological observation, angiography, light and electron microscopy were done. In the clinical study, since September 1996, 22 patients with refractory symptomatic CVS involving 50 vascular territories received dilation therapy by PTA and IAP within 24 hours of clinical neurological deterioration. Results In the experimental study, all the rabbits except two in the 'the 4th day' group showed angiographic dilation in all of the spastic basilar arteries, and neurological improvement; in the ' the 7th day' group angiographic dilation appeared in 4 (57. 1% ) out of 7 rabbits. After 24 hours, 1 rabbit in each group had recurrence of neurological deficits and angiographic constriction. In the clinical study after aneurysm clipping or endovascular coil embolization was done, within 72 hours of SAH all patients underwent endovascular treatment: PTA alone in 3 cases, IAP alone in 14 cases, PTA and IAP in the remaining 5 cases. All vessel segments were dilated satisfactorily after endovascular treatment. Clinical improvement was significant in 13 cases,moderate in 7, minimal or none in 2; 2 cases died on the 7th day after endovascular dilation treatment. Conclusion Endovascular dilating techniques, namely, PTA, IAP and a combination of PTA and IAP, are safe and effective for treatment of symptomatic CVS refractory to medical therapy.