Recent progress in the investigations on improved confinement modes and plasma current profile control on JT-60U is described. The confinement improvement in the high- beta p mode has been found to come from a formation of an internal transport barrier at the q(r) approximately 3 flux surface. Inside of the transport barrier, ion thermal diffusivity is reduced significantly. In contrast to the ion thermal diffusivity, reduction in electron thermal diffusivity is not evident. Preliminary result of a new approach in JT-60U to evaluate local diffusivity with a density fluctuation analysis shows a qualitatively good correlation between the evaluated local diffusivity and the confinement modes: the H-mode and the L-mode, From the viewpoint of the particle control in a tokamak reactor, particle confinement and helium transport in improved confinement modes have been investigated intensively. Particle confinement time of the main plasma in H-modes is found to be less than twice the value of the energy confinement time; the value of particle confinement time is in the acceptable range. Helium transport study shows that the helium concentration into the core plasma will not be so serious in ELMy H mode discharges, because the value of the diffusivity is about 1 m2/s with a peaking parameter of 1 approximately 1.5.