The metabolic fate of ammonium salts of synthetic phosphatidic acids (PA) labelled with 32P (32P-PA) was investigated after their per os administration to rats. It was shown that PA are totally metabolized in the intestine as they cannot be detected in feces if they are applied in doses up to 1.5 g/kg body weight. Increases in the concentration of PA and other phospholipids were not found in organs of experimental animals after administration of 32P-PA per os. 32Pi has a rapid metabolic turnover and therefore its secretion from the organism occurs within 3–7 days, depending on the amount of 32P-PA applied. From a biochemical viewpoint, it appears that there should be no objection to the application of synthetic PA as emulsifiers in food technolog