[en] The study group whose effort is presented here concluded that the United States urgently needs to have a breeder option available for possible deployment before the year 2000 primarily because of uncertainties in the availability of fossil fuels and uranium supplies. It was recommended that the U/Pu LMFBR program proceed as planned, including prompt construction of the CRBRP and its associated fuel cycle facilities. Alternative cycle studies should be pursued, but without significantly delaying the current program. There are technological choices which, in suitable political contexts, may somewhat reduce proliferation risks; of these, only those that employ breeders preserve the breeder option (and the nuclear option in the long term. These alternatives must be coupled with political agreements to have any significant effect on proliferation potential internationally. These same political agreements should suffice to control the U/Pu breeder cycle; there is only a difference in degree between the U/Pu and the denatured Th/U-233 cycles