Abstract: The needle head assembly is used with an ISO luer lock or luer slip syringe having a single thread or multiple threads. The assembly includes a one or two piece luer needle housing having a plunger end, a needle end and a pair of opposing slots located at the needle end thereof. A plunger is axially movable relative to the upper end of the luer needle housing. A needle holder assembly is located in the needle end of the needle housing, with the holder assembly including a bridge fixed in the needle end of the needle housing. The bridge includes a needle holder that has portions extending in opposite directions from the bridge. A diaphragm with a center aperture is sleeved over one of the portions of said needle holder which faces the plunger end of the needle housing. The needle holder has a center passage which permits a needle to be inserted and secured in position at the time of assembly.