Experiments in JET have concentrated on steady state discharges with internal transport barriers (ITBs). The ITBs are formed during the current rise phase of the discharge with low magnetic shear ( = r/q(dq/dr)) in the centre and with high additional heating power. In order to achieve stability against disruptions at high pressure peaking, which istypical for ITB discharges, the pressure profile can be broadened with an H mode transport barrier at the edge of the plasma. However, the strong increase in edge pressure during an ELM free H mode weakens the ITB owing to a reduction of the rotational shear and pressure gradient at the ITB location. In addition, type I ELM activity during the H mode phase leads to a collapse of the ITB with the input powers available in JET (up to 28 MW). The best ITB discharges are obtained with input power control to reduce the core pressure, and with the edge pressure of the plasma controlled by argon gas dosing. These discharges achieve steady conditions for several energy confinement times (τE) with H97 confinement enhancement factors (τE/τE,ITER97 scaling) of 1.2-1.6 at line averaged densities ofaround 30-40% of the Greenwald density. Increasing the density by using additional deuterium gas dosing or shallow pellet fuelling leads to a weakening of the ITB. In order to sustain ITBs at higher densities, type III ELMs should be maintained at the plasma edge, giving scope for future experiments in JET.