The ITER Conceptual Design Activity (CDA) was a three-year, 400 professional-year effort to design a next step tokamak. The activity was conducted under the auspices of the IAEA jointly by EURATOM, Japan, the USSR and USA. The main ITER parameters are summarized in the paper. An engineering design phase (EDA) lasting 5–6 years is planned to begin in 1992. Fuel Cycle design studies carried out as part of the CDA concluded that suitable options existed or could be developed to satisfy all tritium-handling requirements for the machine within the EDA time and resource framework. During the EDA, special emphasis will be required on design integration and optimisation.