Lipid synthesis was investigated in bovine lens in organ culture for 9 hours using C acetate as a precursor. The greatest incorporation occurred in phospholipid fraction with phosphatidyl choline being the major phospholipid labeled. Considerable activity was incorporated in the free fatty acid fraction, cholesterol and cholesterol intermediates. A comparison of the lipid synthesis in bovine, mouse and rabbit lenses showed the rabbit lens to be the most active, the adult mouse lens to be the least active and the bovine and young mice to be intermediate in value.