The JET Lower Hybrid Current Drive (LHCD) prototype system has been in operation in the early part of the 1991 experimental campaign with generated power up to 2.7MW at 3.7GHz and coupled power to the plasma up to 2.4MW. Experiments have focussed so far on the determination of the performance limits of the system, both in terms of long pulse operation and of replacement of the ohmically driven plasma current. Further experiments have also been carried out to confirm early findings of central electron heating induced by LH when applied in combination with Ion Cyclotron Resonance Heating (ICRH).