The effects of ultrasonic (cavitation) melt treatment (UST) on the structure and properties of cast and worked aluminium alloys are considered. The cavitation processes occurring in the melt under cavitation treatment facilitate degassing, fine filtration and nondendritic solidification. The decreased amount of hydrogen and nonmetallic inclusions and the ultimately refined grain structure of cast metal considerably improve mechanical properties of cast billets and deformed semiproducts. The application of UST to hypereutectic Al-Si alloys essentially affects the spatial solidification of primary silicon and assures the formation of cast structure suitable for further deformation.