The characteristics of fast reactors having molten fuels consisting of uranium and plutonium trichlorides dissolved in alkali chlorides and alkaline-earth chlorides were studied. The study included considerations of the physical and chemical properties of the fuel, the heat-removal problems, and neutronic characteristics for three types of chloride reactors: a homogeneous reactor and two internally cooled reactors. Optimization of the core size for 1000-MW(e) reactors resulted in a core volume of 10 000 liters for each type. These reactors have the favorable characteristics (even for natural chlorine) of high breeding ratio, large negative temperature coefficients of reactivity, and low fuel-cycle costs. However, the unattractive characteristics of large plutonium inventory, large volume, complex design, and container material problems indicate that a sizeable program to develop chloride-fueled reactors