[en] The reversibility principle is a way of leaving all options open for future generations. The reversibility principle has been applied in the design of the CIGEO project dedicated to the geological disposal of high-level radioactive wastes. Reversibility means the possibility to stop CIGEO at any moment, it implies the possibility of sealing a burial tunnel even if it is not completely full, or the possibility to recover waste packages from burial. Experience shows that reversibility has to be taken into account as soon as the design stage of the facility. The cost of recovery for a package will be all the more important as the time of being buried has been long. In any case reversibility can not be done at the expense of safety. (A.C.)