Four peripheral vasodilators - tolazoline HCl (Priscoline), nicotinic acid, nicotinyl alcohol (Roniacol), and nylidrin HCl (Arlidin)-were studied in 203 patients over a 13-year period as treatment for macular degenerative changes in the eye.Visual acuity was improved or maintained in 87%. Excellent results were obtained in the treatment of macular edema following cataract surgery and in older patients with diabetic retinopathy. In 126 out of 145 patients with senile macular degeneration, improvement or stabilization was obtained.For all the types of macular degeneration, nylidrin HCl was the most effective of the drugs studied and had the fewest side effects.A recent report based upon animal experiments advises against the use of peripheral vasodilators in degenerative arterial diseases of the eye; however, the assumption made therein that blood volume is a measure of blood flow cannot be accepted. Peripheral vasodilator therapy, which long-term clinical study has shown to be valuable in the treatment of macular degeneration, should not therefore be denied to these patients.