Abstract: This invention discloses a method and apparatus for determining the hardness of a solid workpiece. An elongated rod is excited to be mechanically resonant along its longitudinal axis and is provided at its front end with a defined contact surface of hard material (Vickers diamond). When the rod is rendered resonant at its natural frequency of vibration .omega.o, the contact surface of the rod is pressed into the surface of the workpiece, whose hardness is to be determined, under a predetermined engagement force while the rod is forcibly maintained oscillating at the frequency .omega.o. A sensor coupled to the rod provides a signal indicative of the amplitude of vibrations of the rod when in forced contact with the workpiece and such signal is fed to a computing device for providing a value indicative of the hardness of the workpiece.