The 14-MeV neutrons from a controlled DT fusion plasma can potentially be used to produce neutron source multiplication and energy multiplication through fission in a heavy-element blanket surrounding the fusion plasma. Concepts which involve the use of fusion-produced neutrons to ultimately produce fission are generically classed as fusion-fission hybrids. The conceptual purposes of hybrids can be many and varied: to relax the fusion plasma confinement conditions to allow further development of fusion power; to breed fissile material for fission reactors; as a subcritical fission lattice which is more energetic than the pure fusion concept; and the ultimate reduction of radioactive heavy element waste to fission product. The concept of a hybrid is based on an analysis of the neutronic behavior of the blanket. The status of studies of the neutronics analyses of proposed hybrids has been reviewed. These results have been used to determine the need for further development of hybrid technology.