A full cycle of AC tokamak operation, at a plasma current of ± 2MA, has been demonstrated in JET. The plasma purity in the two half­cycles was equal, with an effective ion charge of 2 at an average density of 1.2 1019 m­3. Dwell times between the two plasmas of between 50ms and 6s were obtained. The range of prefill pressure for successful breakdown of the second plasma was between 1.5 and 6.0mPa, comparable to that in normal JET breakdown. Within this rang, breakdown was not significantly affected by gas release from the vessel walls.