AbstractThis paper reviews the present status of development of ITER high heat flux components in the ITER Japanese Home Team. Special emphasis is laid on high heat flux tests of divertor mock-ups developed in JAERI. JAERI fabricated a divertor mock-up with parallel cooling tubes, and tested it in high heat flux test facilities. The mock-up successfully endured a heat load of 5 MW m−2, 15 s for 10 000 cycles, and a heat load of 20 MW m−2, 15 s for 1000 cycles, which are equivalent to the steady-state heat load and the transient heat load of the ITER requirements, respectively. Based on this encouraging result, large mock-ups were fabricated, which have almost the full-length of the ITER divertor plate. For the upper section of the target, where heat fluxes are lower, CVD tungsten is proposed as the armor. Small divertor mock-ups have been fabricated with a 2-mm thick CVD tungsten layer on a copper heat sink to evaluate these fabrication processes. In parallel with those activities, improvement of bonding techniques and armor materials has been carried out, such as brazing with a non-silver braze and development of 3D CFCs.