High power ultrasonic transducers are now used in a wide variety of applications, ranging from medical devices, ultrasonic cleaning, ultrasonic welding and machining to sono-chemistry reactors. Use of ultrasonic transducers for various applications of atomizers, cleaning, sonochemistry and sonoluminescence, surgery, peening of welding joints, forming processes, ultrasonic motor, ultrasonic lubrication and nondestructive evaluations show the wide range of this growing technology in science and engineering. This work presents essential information, and shows the wide range of engineering & scientific applications for them.