Abstract: Biomedical device for carrying out an arterial catheterization comprising a catheter assembly, a Seldinger assembly, an outer sheath assembly configured to contain thereinside both said catheter assembly and said Seldinger assembly when the device is assembled before its use, at least a cannula-needle integral to the Seldinger assembly, valve means to avoid blood backflow and safety means for needle clamping, protection means for the needle, said catheter assembly comprising a thin tube, a nearly cylindrically shaped end provided with a couple of side wings, an inner cavity obtained in said end, said device being characterized in that said valve means and said safety means are located inside said outer sheath assembly in the inner cavity obtained in said cylindrical seat of the catheter assembly.