An improved male luer connector assembly including a central elongated male luer connector tapering from a distal end to a locking collar disposed approximately at the mid-point of the connector. A recessed section is disposed between the first collar and a second collar. Locking teeth are disposed on a proximal face of the locking collar in spaced relation. A threaded lock nut is mountable on the male luer connector. An inner peripheral end wall of the lock nut surrounds the male luer connector and carries a ratchet at an inner end face thereof. In the connection of the male luer connector assembly to a complementary female threaded luer connector, the engaging teeth on the proximal face of the locking collar are drawn into engagement with the ratchet on the inner face of the lock nut to ensure and maintain a locking fluid-tight connection between said male luer connector assembly and the female luer connector.