Ethepon is used commercially in Israel to facilitate mechanical harvesting or hand picking of olive fruits, but the results are often not satisfactory, due to insufficient reduction of the fruit removal force. Studies with 14C-ethephon were carried out to follow the fate of the applied ethephon from treatment until fruit harvest and to determine the actual uptake and efficiency of the sprayed compound. Only a small portion (less than 3%) of the applied ethephon actually penetrated the target tissue i.e. the pedicels, and released the ethylene responsible for promoting fruit loosening. There was almost no translocation of ethephon from other organs (leaves, fruits) to the fruit pedicels. Extended imbibition in the ethephon solution increased ethephon uptake, which was also enhanced by higher ambient temperatures. Penetration of ethephon varied among different tissues (leaves, fruits and pedicels). Field applications enabled some calculations of the relationship between the amount of ethephon applied and that actually required to achieve proper fruit loosening.