Recent exper:iments on JET with increased additional power have resulted in plasma parameters close to those of a thermonuclear reactor. Electron and ion temperature achieved at a plasma density of 2x1019m-3; transiently, during an H-mode the fusion product (niTiτE) has reached 3x1020m-3keV.s at temperatures exceeding 5keV; and plasma current up to 7MA (for 2s) have been achieved. However, degradation of confinement with increased power is observed in all regimes.