Evidence is presented to show that cereal grain phytic acid has the myoinositol hexaorthophosphate structure suggested by Anderson and not the hydrated myoinositol tripyrophosphate structure proposed by Neuberg. DL-Myoinositol 1,6:2,3:4,5-tripyrophosphate which is structurally related to the Neuberg formulation has been prepared. The "phytic acid" fraction from chicken blood has been shown to be predominantly 1,3,4,5,6-myoinositol pentaphosphate. The structures assigned to these compounds have been confirmed by 31P nuclear magnetic resonance.