Precocious metamorphosis was induced by topical appilication of a terpenoid immidazole Compound, KK-42, immediately after the 3rd larval ecdysis of Bomyx mori. All the larvae recieved 5 to 300μg of compound become trimolting pupae. Dose effects of KK-42 upon the egg formation in the induced trimolter were investigated. 1. The number of matured eggs produced was ca. 40% that produced by the normal tetramolting control, although there observed no dependency on the dose of applied KK-42. 2. The size and the weight of eggs produced by the trimolter were significantly smaller and lighter than normal tetramolter's eggs. Higher dose gave smaller values. 3. The amount of yolk proteins decreased according to the increasing dose of KK-42. However, there were no qualitative changes of the yolk proteins as analysed by gel electrophoresis. 4. It is inferred that a large amount of KK-42 affects oogenesis through the functional alteration of the ovarian folliclar epithelial cells.