After integration of chronological factors according to Ellis' formula and of B.R.E. for various energies of radiation, the reference dose at the deep limit of the tumor and the surface hyperdosage are kept constant. The values which have been adopted after a very large clinical experience are the following: --reference dose: 6000 rads (N.S.D. 1760). --surface dose: 8400 rads (N.S.D. 2200). The choice of the energy of radiation is the only variation, depending on the thickness of the tumor. A few schemes of equivalent chronological factors are presented, giving less than 1 p. 100 risk of recurrence and a small risk of late radiolesions for normal tissues.