This subject examines the basic physics, instrumentation and some clinical aspects of medical diagnostic ultrasound. The propagation of ultrasound in an attenuated media, the instrumentation associated with different ultrasound modalities, common imaging artifacts, potential bioeffects, and recommendations for the safe use of ultrasound are all considered. In addition, aspects of 2D real-time greyscale imaging as applied to selected clinical areas, including abdominal, obstetric and gynecological ultrasound, are covered. The interpretation of diagnostic information gained from the various ultrasound modalities is also given attention.