The parameters of protein metabolism, such as the levels of soluble, structural and total proteins, free amino acids, and the activity levels of protease, aspartate and alanine aminotransferases and glutamate dehydrogenase were assayed in the hemolymph, silk-gland, muscle and fat-body on different days of the 5 th instar larva of the silkworm, Bombyx mori, following exposure of the silkworm eggs to 1 MHz continuous wave of ultrasound at an intensity of 9W/cm 2 for 2 minutes. Ultrasound was found to promote the accumulation of proteins, which include silk proteins as well, while retarding proteolysis and turnover of proteins towards the release of amino acids, keto-acids etc. Changes in the levels of these biochemical constituents are correlated with the events of histogenesis and histolysis associated with metamorphosis. It may be inferred that protein metabolism is stimulated by ultrasound, resulting in greater turnover of silk proteins, spinning activity and silk output.