Abstract: A blood collection system comprising a needle assembly, an evacuated collection tube and a holder for said tube. A housing at the end of said holder receives an adaptor therein. A conventional cannula assembly is threaded into the adaptor such that the rear cannula end extends into the collection tube with the front cannula end extending forwardly for venipuncture. A locking assembly traversing the housing includes first and second slide locks with apertures therein. The slide locks have a first biased position in which portions of the adaptor are engaged by the rims of the apertures to hold the cannula within the housing. Upon user manipulation of the locks, the slide locks are moved to disengage the rims from the adaptor. The latter movement causes release of the adaptor with cannula assembly from the housing allowing for cannula disposal subsequent to use without user handling.