A method and apparatus for non-intrusively measuring flowing currents and/or voltage on the inner conductor of a coaxial cable is introduced herein. In particular, a resultant low-impedance element is coupled concentrically to the shield at a desired insertion point of the coaxial cable. A pair of conductive leads provided by the resultant low-impedance element is thereafter monitored for derived flowing currents that are in direct proportion to but of opposite polarity to the current within the inner conductor of the coaxial cable.