Shape casting using ultrasonic processing was historically the first commercial application of ultrasonic treatment, as witnessed by two monographs published in 1965 [1] and 1967 [2] that described the technological schemes and practical experience in investment casting of aluminum alloys. The advantage of using ultrasound in investment casting lies in the relatively small volumes that are required to be processed. On the other hand, the ultrasonic treatment during solidification is applicable only to small castings; otherwise, issues with structure uniformity may arise. Ultrasonic processing for casting large parts should be performed using one of the ex-mold schemes when the liquid metal rather than the semisolid slurry is treated. Different mechanisms are involved, depending on the technological scheme (see Chapter 5).