A combination of a drug infusion device and a syringe, - wherein the syringe comprises: - a substantially cylindrical body which may be filled with a liquid drug, said body having at a first end or base, a pair of tabs for coupling the syringe to infusion device through rotation and, at the opposite end, a terminal for mounting a needle or a cannula for administering said liquid drug; - wherein the infusion device comprises: - a housing which accommodates an electric motor and corresponding mechanical means for axially displacing a pusher that pushes the plunger of syringe mounted in said infusion device and containing a drug so as to gradually deliver said drug contained in the syringe, as well as an electronic control device arranged to adjust the rate and the duration of drug delivery and other parameters of the infusion device; - a ring nut provided in correspondence with one base of housing for coupling syringe with infusion device, said ring nut being interrupted to allow inserting syringe on base of housing, and defining with said base a pair of diametrically opposite slots where tabs of syringe can be inserted by rotating body of syringe about its axis; characterized in that the syringe further has, in correspondence of base, at least one locator arranged to abut against the side wall of said ring nut when syringe is properly positioned, with tabs properly located in slots, whereby said at least one locator prevents any further rotation of body of syringe.. - wherein the syringe comprises: - a substantially cylindrical body which may be filled with a liquid drug, said body having at a first end or base, a pair of tabs for coupling the syringe to infusion device through rotation and, at the opposite end, a terminal for mounting a needle or a cannula for administering said liquid drug; - a substantially cylindrical body which may be filled with a liquid drug, said body having at a first end or base, a pair of tabs for coupling the syringe to infusion device through rotation and, at the opposite end, a terminal for mounting a needle or a cannula for administering said liquid drug; - wherein the infusion device comprises: - a housing which accommodates an electric motor and corresponding mechanical means for axially displacing a pusher that pushes the plunger of syringe mounted in said infusion device and containing a drug so as to gradually deliver said drug contained in the syringe, as well as an electronic control device arranged to adjust the rate and the duration of drug delivery and other parameters of the infusion device; - a ring nut provided in correspondence with one base of housing for coupling syringe with infusion device, said ring nut being interrupted to allow inserting syringe on base of housing, and defining with said base a pair of diametrically opposite slots where tabs of syringe can be inserted by rotating body of syringe about its axis; - a housing which accommodates an electric motor and corresponding mechanical means for axially displacing a pusher that pushes the plunger of syringe mounted in said infusion device and containing a drug so as to gradually deliver said drug contained in the syringe, as well as an electronic control device arranged to adjust the rate and the duration of drug delivery and other parameters of the infusion device; - a ring nut provided in correspondence with one base of housing for coupling syringe with infusion device, said ring nut being interrupted to allow inserting syringe on base of housing, and defining with said base a pair of diametrically opposite slots where tabs of syringe can be inserted by rotating body of syringe about its axis;