The current status of knowledge regarding low rate telecobalt irradiation does not permit any definitive conclusions. However, it has shown that this technique of irradiation, on condition that it is given in two fractions separated by three weeks, is without major risk for healthy tissue, the tolerance of skin being particularly remarkable, and with immediate very satisfactory results on the tumour. Strict statistical comparison will be necessary, however, if a final judgment is to be made. Thus a study group of the O.E.R.T.C. has decided to undertake a comparative study between classical fractioned irradiation and semi-continuous low rate irradiation. The trial involves only cancers of the base of the tongue he has began in January 1976.