Thorium is being touted as a potential wonder fuel. Proponents believe that this element could be used in a new generation of nuclear-power plants to produce relatively safe, low-carbon energy with more resistance against potential nuclear-weapons proliferation than uranium. Although thorium offers some benefits, we contend that the public debate is too one-sided: small-scale chemical reprocessing of irradiated thorium can create an isotope of uranium that could be used in nuclear weap-ons, raising proliferation concerns.