This paper describes a study of the use of ultrasound to measure the pressure between two machine elements in contact. Relationships between ultrasonic reflection coefficient and pressure have been found both empirically and via a numerical contact model. The numerical contact model was used to predict the stiffness of the interface. This stiffness was then converted to ultrasonic reflection coefficient via a quasi-static spring model. The quasi-static spring model was shown to be valid for surface finishes in the range 0.5-2.1 μm and ultrasonic frequencies up to 31 MHz. Ball-flat contacts, similar to those found in contacting machine elements, were scanned using a focused ultrasonic transducer. Using the relationship between ultrasonic reflection coefficient and pressure, the contact pressure distribution over the contacts was found. Very good agreement was found between the calculated contact pressure distribution and that predicted by Hertzian contact theory, indicating that ultrasound is a viable method for measuring the contacts in real machine elements, both at the prototype development stage and in situ.