Guidewires for microcatheters used for the subselective catheterization of small vessels must meet high quality requirements in regard to handling, steerability, radiopacity and physical properties. The aim of this paper is to classify one of the factors that determine the physical and mechanical parameters of a number of existing microcatheter guidewires. A torsion-testing equipment for guidewires was devised. Nitinol wires were tested and compared with the austenitic stainless steel variants. 13 different commercial wires were tested. Tensile strength, shear modulus and wire diameter are the determining factors of the torsional rigidity of guidewires. By interpreting the measured torsional momentums various statements concerning the torsional rigidity of different wires can be made. The properties of guidewires are characteristic features of a system and friction and flexible strength examinations have to be carried out to design new variants of wires to meet the requirements of interventional physicians.