The efficacy of using hydrodistention and vasodilatory drugs to relieve spasm in arteries was investigated. The femoral arteries of 64 rabbits (divided into five groups) were placed in spasm by the topical application of epinephrine (1 mg/ml). In group A (controls) vasospasm was induced without further treatment. In group B vasospasm was induced, and the arteries were hydrodistended with normal saline. In three additional groups vasospasm was induced and either 10% lidocaine hydrochloride (group C), verapamil hydrochloride (group D), or chlorpromazine hydrochloride (group E) was applied. Thirty minutes later the vessels were hydrodistended. All vessels were measured at set intervals, and some specimens were retained for light and electron microscopy. All methods of spasm relief were successful, although to varying degrees. Hydrodistention alone produced the widest dilation for the longest time. Lidocaine was the most successful drug treatment alone. Verapamil followed by hydrodistention was the most successful combination regimen, but did not produce better results than hydrodistention alone. Hydrodistention alone produced significant arterial wall damage, resulting in permanent structural modifications. Prior vasodilatory drug treatment reduced but did not eliminate hydrodistention damage. Although hydrodistention dilates for longer periods than vasodilatory drugs, the arterial wall damage associated with hydrodistention indicates that it should be used only when all other methods of vasodilation have failed.