The riboflavin levels in liver, kidney and small intestine of mice, administered with Ca-salt, such as Ca-gluconate, CaCl_2 or CaCO_3,and calciferol were observed. When the Ca-salts were given the riboflavin contents of kidney and small intestine showed moderate decrease, but there was no change in the liver. When calciferol was given with Ca-gluconate, the decrease of riboflavin contents by Ca-salt could be prevented, especially kiney showed a higher value than that of control organs.
