Abstract: Apparatus for the safe use and disposal of a syringe includes a needle guard for covering the needle of the syringe. The needle guard is slidable between retracted and extended positions. Biasing structure is adapted to urge the needle guard over the needle. The needle guard slides to the retracted position, in opposition to the biasing structure, for injecting a subject, and slides over the needle as it is withdrawn from a subject in response to the biasing structure. Structure for locking the needle guard in the fully extended position upon complete withdrawal of the needle from the subject is also provided. A cam member is preferably provided with cam surfaces and engagement portions which cooperate with cam control surfaces to effect retention of the cam member in a retracted position during a filling operation, and locking of the needle guard over the needle for disposal.