Abstract. Heliotron J is a flexible, concept-exploration facility ( R0 = 1.2 m, B(0) < 1.5 T) aiming at experimentally optimizing the helical-axis heliotron concept. This paper reports the Heliotron J experiments with special regard to the characteristics of ECH plasmas. The experiments have presented the following results. (1) The energy confinement time was comparable to the ISS95-value. No significant degradation of the density dependence of the electron temperature was observed even in the « 0.1 regime. It was also suggested the existence of discharges with more preferable confinement property. (2) A new effective heating region was found for 53.2GHz ECH in the higher magnetic field (B(0) 1.4-1.5 T), where there are no resonance layers for electromagnetic waves in the core region. (3) The configuration effects of plasma confinement were observed. (4) Unexpected up-down asymmetry was found in the profiles of diverted plasma density and floating potential at the geometrically up-down symmetric divertor legs.