This standard provides definitions for the transmitted field characteristics of focusing transducers for applications in medical ultrasound; relates these definitions to theoretical descriptions, design, and measurement of the trans-mitted fields of focusing transducers; gives measurement methods for obtaining defined characteristics of focusing transducers and specifies beam axis alignment methods appropriate for focusing transducers. This standard relates to focusing ultrasonic transducers, operating in the frequency range appropriate to medical ultrasound (0.5 MHz - 40 MHz) for both therapeutic and diagnostic applications.#,,#