IN 1944 indandione derivatives were reported by Kabat, Stohlman and Smith1 to be capable of producing hypoprothrombinemia in laboratory animals. These workers studied several compounds with different side chains, but only 2-phenyl-l, 3-indandione was found to have a hypoprothrombinemic effect comparable to that of Dicumarol. In their experience compounds with 3 ketone groups were more effective in producing hypoprothrombinemia than those with 2 ketone groups. In 1947 Meunier, Mentzer and Molho,2 during a study of chemical structures possessing activity against vitamin K, reported phenyl indandione or 2-phenyl-l, 3-indandione to be effective in its hypoprothrombinemic action in laboratory animals; its formula . . .