Strontium absorption was studied in vivo with loops of ileum in rachitic chicks and found to be increased by vitamin D(3), bile salts and sodium lauryl sulphate. 2. Bile salts and sodium lauryl sulphate rendered strontium soluble in butanol-benzene (1:1, v/v). 3. Bile was not concerned in the absorption of iron in rats from its water-soluble form, ferrous sulphate. 4. Ligation of the bile ducts in rats caused a decrease in the absorption of iron presented as its sparingly soluble phosphate. 5. The effect of bile on cation absorption is discussed.