Diaphragm ultrasonography offers a feasible non-invasive way to assess both structure and function of this primary muscle of respiration. Diaphragm ultrasound imaging provides diagnostic and prognostic information that can assist with clinical decision-making. This chapter summarizes the practical aspects of the technique, describing how to perform an objective and standardized assessment with specific considerations and caveats of each measurement. The evidence in support of this practice, current and emerging, is briefly discussed.