Abstract: A method of calibrating an ultrasound probe having a coupling element for engaging the surface of an object to be inspected, in which the ultrasound probe and a calibration artefact are provided on a positioning apparatus having at least one axis about which the relative orientation of the ultrasound probe and calibration artefact can be changed, the method including, in any suitable order: i) for a plurality of different relative orientations between the ultrasound probe and the calibration artefact about the at least one axis, measuring the signal received by the ultrasound probe; and ii) from the measurements, determining at least one calibration parameter which is indicative of at least one axis of optimum signal of the ultrasound probe, and recording the at least one calibration parameter for subsequent use.