Abstract 1. 1. Male Japanese quail, Coturnix coturnix japonica (35 days of age) were kept for 35–45 days under 16L:8D (16hr light:8hr dark) or 8L:16D (8 hr light:16hr dark). 2. 2. Weight of liver, and content of glycogen and lipid per g liver of quail (70–80 days of age) under 8L:16D were significantly higher than those under 16L:8D. 3. 3. The respective activity per mg protein or g liver of glucose 6-phosphate dehydrogenase, malic enzyme, lactate dehydrogenase, NADP-isocitrate dehydrogenase, succinate dehydrogenase and choline dehydrogenase in liver from quail under 8L:16D was significantly higher than under 16L:8D, while the activity of cytoplasmic l-glycerol 3-phosphate dehydrogenase was significantly higher under 16L:8D than under 8L:16D. 4. 4. Concerning kidney enzymes, no significant difference was obtained for most of the enzymes examined except succinate dehydrogenase, and choline dehydrogenase which were significantly higher under 8L:16D than under 16L:8D.