To the Editor:— Attention should again be called to the wellknown physiological phenomenon of vasodilatation following the application of heat. In patients who have been subjected to repeated intravenous procedures veins often become difficult to find. The application of heat by immersing the hand in a basin of hot water for five minutes or applying a hot water bottle at the antecubital fossa often solves the problem of inserting a large caliber needle into a small vein. This procedure seems too simple to mention, but the difficulty experienced by all of us at times in intravenous medication makes any aid valuable.