Abstract: A blood vessel entry indicator device is provided which includes a colored flexible membrane disposed within the transparent body of a hypodermic needle that is stretched over the proximal end of the needle cannula. As the needle reaches the inside of the blood vessel, pressure within the vessel is transferred through the cannula to the membrane which moves or inflates indicating that entry has been achieved. A stopper is provided for arterial use. Because it is pressure sensitive, the invention provides a positive indication of blood vessel entry, avoiding double puncture of the same blood vessel.