AbstractThe JT-60 project concentrates research efforts to contribute to the ITER EDA and to establish the basis of a steady-state tokamak reactor. Negative shear, as well as high-βp-mode, are the major operation schemes in the recent JT-60 experiments. Equivalent-QDT=1.05 with a negative shear discharge and the fusion triple product nD·τE·Ti=1.5×1021 m−3·s·keV with a high-βp H-mode have been achieved. A high recycling and strong radiative boundary plasma has been obtained in negative shear high confinement discharges. Long sustainment of high performance discharges has satisfied the conditions required for a steady-state tokamak reactor concept such as SSTR. JT-60 started operation in 1985 and had a significant modification to JT-60U in 1989–1990. The most frequent machine troubles occurred due to control software bugs, air-leaks of the vacuum vessel, and electric insulation breaks in the tokamak machine. Machine behaviors beyond our expectations have been the strong membrane vibrations of the vacuum vessel in the original machine JT-60, the cooling water leaks from the TF coils, divertor tile breaks due to halo current, and the cooling pipe damages due to high energy electrons penetrating under the divertor tiles. These should be considered the important engineering issues even with regard to future fusion research.