Abstract: Changes of the phosphate compounds and the incorporation of radioactive phosphate into various phosphorus-containing compounds in both developing and abscissing fruits of ‘Tompkins King’ apple were investigated in 1962–1964. It was found that in abscissing fruits, the contents of inorganic phosphates were higher, while those of organic phosphates were lower than in developing fruits. The activity of ATPase was also lower in abscissing than in developing fruits. Experiments with p32-labeled phosphate indicated that the uptake of p32 by abscissing fruits was much less active than by developing fruits. There was more radioactivity in sugar-phosphates, high-energy nucleotides, phospholipids, nucleic acids and phosphoproteins in developing than in abscissing fruits. Similar results were obtained in fruit flesh and in seeds. The above results suggest that the shortage of food supply and the low level of phosphorylation in young fruit may cause suppression in fruit growth and alteration in normal metabolic pathway, which in turn may eventually bring about the senescence and abscission of the young fruits.