In Japan Atomic Energy Research Institute (JAERI), a demonstration program on hydrogen production has been undertaken just January in 1997, as a research and development entrusted from Science and Technology Agency. Using nuclear heat (10MW, 905 degreesC, 4.1MPa) supplied by the High Temperature engineering Test Reactor (HTTR), a hydrogen production system is being designed to be able to produce hydrogen with the production rate of approximately 4000 Nm(3)/hr, which is in a range of commercial level, by a steam reforming of natural gas. The safety principle and standard are also being investigated for nuclear heat utilization systems connected to High Temperature Gas-cooled Reactors (HTGRs) including the HTTR. The HTTR hydrogen production system is first connected to a nuclear power reactor, hence an out- of- pile test, a hydrogen permeation test and a corrosion test of a catalyst tribe of the steam reformer are carried out prior to the demonstration test of the HTTR hydrogen production system. In order to confirm controllability, safety, and performance of key components in the HTTR hydrogen production system, the facility for the out- of- pile test is being designed and manufactured on the scale of approximately one thirtieth of the HTTR hydrogen production system. It is equipped with an electrical heater as a heat source instead of the HTTR. The out- of- pile test will be started from 2000 and will be performed for 4 years. Check and Review of the demonstration program in the HTTR will be made in 2000 from the view point of economy and technology, then the HTTR hydrogen production system will be constructed from 2001 and will be demonstratively operated from around 2005 to 2010. The hydrogen/tritium permeation test is carried out from the next year to obtain the data on hydrogen /tritium permeation coefficients for mainly the Hastelloy-XR, which is a nickel-base helium corrosion- and heat- resistance super alloy and is used in high temperature components of the HTTR and the HTTR hydrogen production system, and to verify the reduction method of the hydrogen/tritium permeation through the tube wall to the helium coolant. In the material test, characteristics of the corrosion due to metal dusting and the strength reduction due to hydrogen embrittlement are examined with the Hastelloy- XR material and so on in an atmosphere of reforming gases of CH4, H2O, CO, CO2, H-2 from this year. The overview is reported on the demonstration program of the hydrogen production in HTTR.