Materials issues related to the Force-Free Helical Reactor (FFHR) design are presented. In FFHR, which uses the Flibe liquid breeder from the main reason of safety, if there is no need to replace in-vessel materials in the lifetime of 30 years, the reactor can be operated with not only the high safety margin but also a high availability of the plant, resulting in reducing not only the cost of electricity (COE) but also the total amount of radiative wastes. Nuclear properties of induced radioactivity, solid transmutation products, and decay heat at the 14 MeV neutron fluence of 45 MWa/m(2) as well as materials compatibility with Flibe are investigated for JLF-1, V-alloy, SiC and high Z materials. In conclusion, control of metal impurities, transmutation of W and V, acceptable decay heat, and reaction kinetics with Flibe are pointed out as R&D issues. (C) 1998 Elsevier Science B.V. All rights reserved.