Under normal conditions the rate of the 32P-orthophosphate incorporation into the polyphosphoinositides was 30--40 times greater than into the other phospholipid fraction of the normal rat liver. There was a rapid postmortem alteration of the polyphosphoinositide content in the liver. Under conditions studied the changes in the phospholipid content were revealed in the polyphosphoinositide fractions only. The changes in the content and in the metabolic intensity of rat polyphosphoinositide in the liver were in many respects similar to those in the brain. Polyphosphoinositide fractions were found to be the most labile of all the phospholipid fractions in the rat liver.