The first tokamak discharges with deuterium-tritium mixtures have been carried out in the Joint European Torus (JET). The main objectives were to produce more than IMW of fusion power in a controlled way, to determine tritium retention in torus systems and to establish effective means of tritium removal. The experiments were undertaken within limits imposed by restrictions on vessel activation and tritium usage. Deuterium plasmas were heated by high power deuterium neutral beams from fourteen sources and fuelled by two neural beam sources injecting tritium. In the best (D-T discharge), the tritium concentration was about 11% at peak performance, when total neutron emission rate was 6.0*1017 s-1, with 1.7 MW of fusion power. The fusion amplification factor QDT was 0.15. With optimum tritium concentration, this pulse would have produced a fusion power approximately=5 MW and nominal QDT=0.46. The same extrapolation for the best pure deuterium discharge gives about 11 MW and a nominal QDT=1.14. Techniques for introducing, tracking, monitoring and recovering tritium were highly effective.