Safety assembly for the reconstitution, the taking or the infusion of pharmacological liquids, comprising: - a needle-less syringe, comprising an axial duct in communication with an opening, and coupling means in correspondence of said opening; and - a safety device comprising: - first coupling means configured in such a way to be coupled with said coupling means of the syringe in such a way to fix the safety device to the syringe, second coupling means, - an axial duct, that extends from the first coupling means to the second coupling means, and - a first and a second membrane (31, 32) disposed inside said axial duct; each membrane (31, 32) being provided with a through hole (F1, F2) and being in a non-compressed closed position wherein the hole of the membrane is closed and obstructs the passage of liquid in the axial duct, and in a compressed open position, wherein the hole of the membrane is open and does not obstruct the passage of liquid in the axial duct; each membrane (31, 32) having a channel (310, 320) in communication with said through hole (F1, F2); said safety assembly also comprises: - first compression means associated with said coupling means of the syringe to compress the first membrane to the compressed open position, when the coupling means of the syringe are coupled with said first coupling means of the safety device; and - second compression means comprising a cannula slidingly mounted into the axial duct of the safety device to compress the second membrane in the compressed open position; said cannula comprising an ending portion and a tip; characterized in that said safety assembly also comprises a user device comprising an axial duct in communication with an opening and coupling means in correspondence of said opening, said user device having a needle for the injection of a pharmacological fluid to a user or being connected to a receptacle for the administration/infusion of the pharmacological fluid; the safety device comprising the second coupling means configured in such a way to be coupled with the coupling means of the user device in such a way to fix the safety device to the user device; when said coupling means of the user device are coupled with the second coupling means of the safety device, the ending portion of the cannula is coupled by interference inside the axial duct of the user device and the tip of the cannula is suitable for pushing said second membrane to its compressed open position, enlarging the through hole of the second membrane, without crossing the channels (320, 321) of the membranes (31, 32). - a needle-less syringe, comprising an axial duct in communication with an opening, and coupling means in correspondence of said opening; and - a safety device comprising: - first coupling means configured in such a way to be coupled with said coupling means of the syringe in such a way to fix the safety device to the syringe, second coupling means, - an axial duct, that extends from the first coupling means to the second coupling means, and - a first and a second membrane (31, 32) disposed inside said axial duct; each membrane (31, 32) being provided with a through hole (F1, F2) and being in a non-compressed closed position wherein the hole of the membrane is closed and obstructs the passage of liquid in the axial duct, and in a compressed open position, wherein the hole of the membrane is open and does not obstruct the passage of liquid in the axial duct; each membrane (31, 32) having a channel (310, 320) in communication with said through hole (F1, F2); said safety assembly also comprises: - first compression means associated with said coupling means of the syringe to compress the first membrane to the compressed open position, when the coupling means of the syringe are coupled with said first coupling means of the safety device; and - second compression means comprising a cannula slidingly mounted into the axial duct of the safety device to compress the second membrane in the compressed open position; said cannula comprising an ending portion and a tip; - first compression means associated with said coupling means of the syringe to compress the first membrane to the compressed open position, when the coupling means of the syringe are coupled with said first coupling means of the safety device; and - second compression means comprising a cannula slidingly mounted into the axial duct of the safety device to compress the second membrane in the compressed open position; said cannula comprising an ending portion and a tip; characterized in that said safety assembly also comprises a user device comprising an axial duct in communication with an opening and coupling means in correspondence of said opening, said user device having a needle for the injection of a pharmacological fluid to a user or being connected to a receptacle for the administration/infusion of the pharmacological fluid; the safety device comprising the second coupling means configured in such a way to be coupled with the coupling means of the user device in such a way to fix the safety device to the user device; when said coupling means of the user device are coupled with the second coupling means of the safety device, the ending portion of the cannula is coupled by interference inside the axial duct of the user device and the tip of the cannula is suitable for pushing said second membrane to its compressed open position, enlarging the through hole of the second membrane, without crossing the channels (320, 321) of the membranes (31, 32).