JET's experiments in the 1991-2 campaign produced two sets of discharges where the energy confinement was significantly higher than in the conventional H-mode regime. These types of discharges were: ­ the Hot Ion H-mode pulses, most of which were completed m preparation for the first tritium experiment on JET; and ­ the high-BPOL bootstrap current-dominated H-modes. These discharges have typical confinement a factor 1.5 times higher than the conventional H-mode regime and a factor 3 times higher than the normal L-mode. A general overview of the two regimes is given m section I. The next two sections of this report concentrate on particular aspects of the Hot Ion (HI) H-mode. Section II considers the transition from L mode to H mode in the HI H-modes. Section III covers the termination of the high performance phase in these pulses.