The Tailveiner is the first easy to use mouse and rat restrainer specifically designed for tail vein injections. The slotted tube permits the rat or mouse to be quickly pulled in by the tail. The animal is then restrained by a tapered plug which slides easily to accommodate any size rat or mouse, but locks automatically when handle is released. After dosing, the handle is lifted and the plug is easily removed. The Tailveiner is the fastest restrainer yet for intravenous injections in small animals.