A safety arrangement for a medical needle (15) has a support (14) for carrying the mount end of the needle, and a sleeve (16) slidably mounted on the support (14) for movement from an initial position to a retracted position and then back to a protecting position where the sleeve (16) covers the tip (21) of the needle (15). A spring (32) urges the sleeve towards its protecting position and a blocking member (23) projects forwardly from the support (14) and is movable between non-blocking and blocking positions. In the non-blocking position the sleeve (16) is free to slide from its initial position to its retracted position. On movement of the sleeve to its protecting position, the blocking member (23) moves to lie between the support (14) and sleeve (16) to prevent subsequent movement of the sleeve away from its protecting position. A control mechanism (27) releases the blocking member (23) so that it may move from its non-blocking position to its blocking position, the mechanism (27) being controlled by movement of the sleeve (16) from its initial position at least partway towards its retracted position.Linvention concerne un agencement de sécurité conçu pour une aiguille médicale (15). Cet agencement comporte un support (14) permettant de porter lextrémité de montage de laiguille, et un manchon (16) monté de manière coulissante sur le support (14) de manière à pouvoir se déplacer dune position initiale vers une position rétractée puis de nouveau vers une position de protection où le manchon (16) recouvre la pointe (21) de laiguille (15). Un ressort (32) sollicite le manchon vers sa position de protection. Un élément de blocage (23) sétend vers lavant du support (14) et peut être déplacé entre les positions de non blocage et de blocage. Lorsquil est en position de non blocage, le manchon (16) peut glisser de sa position initiale vers sa position rétractée. Lorsque le manchon est déplacé vers sa position de protection, lélément de blocage (23) se déplace de façon à
