1. Lipid biosynthesis in the liver as well as transport into the follicles in Japanese quail were investigated depending on sexual maturity at 5, 7, 9 and 11 weeks of age. Lipogenesis of the liver and incorporation of lipid into the follicles were determined by administering [1-14C]sodium acetate. 2. Body weight increased up to 9 weeks of age, whereas the weight of the liver and follicle did not alter after 7 weeks of age. 3. Fatty acid synthesis in the liver was at its highest at 7 weeks of age. Incorporation of 14C into non-saponifiable lipid and glyceride-glycerol fractions in the liver was not influenced by aging. 4. The labelled fatty acids in the follicle increased linearly as the birds became sexually mature.