The JET Programme to 1999 concentrates on issues that must be solved before a decision to construct ITER can be taken. The paper discusses three areas representative of the physics support provided: confinement studies, divertor studies and fusion performance. Due to its large size and proximity to reactor conditions, JET provides the most ITER relevant confinement data of all tokamaks. JET has an active divertor programme (Mark I, 1994195; Mark IIA, 1996; Mark IIGB, 1997/98) aimed at developing a viable divertor concept for ITER, based on, for example, the gas target/radiative divertor concept. High performance ELM-free H­ and VH-mode discharges, complemented by quasi-stationary ELMy H-modes in an ITER-like configuration will be developed further in 1994/95 and provide the basis for D-T experiments in 1996 and 1999.