The present version, THARC-S, of the transient thermohydraulic subassembly code, THARC, under development at the Joint Research Centre at Ispra, has been applied to predict the transient thermohydraulic behavior of liquid-metal fast breeder reactor subassemblies subjected to loss-of-flow conditions. Information is given on the present status of development of THARC. Computational results are presented for 217-rod subassemblies, both for grid and wire spacers. It is shown that radial power gradients and overcooling in the region adjacent to the wrapper wall cause boiling inception in the subassembly to be incoherent with, as a consequence, a more gradual boiling and voiding process than expected on the basis of a one-dimensional approach. It is demonstrated that heat capacity effects associated with the fuel rods and the wrapper wall are of considerable importance. Aspects associated with code validation in out-of-pile bundle experiments are also briefly discussed.