The International Thermonuclear Experimental Reactor (ITER) is a collaboration of the European Communities, Japan, the Russian Federation, and the United States of America, carried out under the auspices of the International Atomic Energy Agency (IAEA), in the field of controlled thermonuclear fusion. As such, ITER represents a unique example of international collaboration on a major scientific project. The overall programmatic objective, as defined in the ITER Engineering Design Activities (EDA) Agreement, is to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes. ITER would accomplish this objective by demonstrating controlled ignition and extended burn of deuterium-tritium plasmas, with steady-state as an ultimate goal; by demonstrating technologies essential to a reactor in an integrated system; and by performing integrated testing of the high-heat flux and nuclear components required to utilize fusion energy for practical purposes. ITER, the so-called “next step” device to be built after the present-day tokamaks, will not generate any electric energy. It will be the task of the ITER successor, the “Demonstration” reactor, to generate the first electricity from fusion energy and demonstrate the economic feasibility of fusion reactors. The ITER EDA phase, due to last until July 1998, will encompass the design of the device and its auxiliary systems and facilities, including the preparation of engineering drawings. The EDA also incorporates validating research and development (R&D) work, including the development and testing of key components. During the EDA the site requirements will be established, and the necessary safety, environmental, and economic analyses will be performed. Detailed plans, including cost, manpower, and schedule, will be developed for the construction and assembly of ITER and for operations, maintenance, and decommissioning. In addition, proposals will be developed on approaches for joint implementation of the future construction and operation of ITER, in order to permit a decision about the construction of the reactor to be taken by the four parties by the end of the EDA. During the first 18 months of the EDA, design options derived from the objectives and general principles of the project have been reviewed and a reference design developed. In addition to the continuing activities on design, supporting short- and long-term R&D programs are being defined, and some of these activities have already begun in laboratories and industries in the countries that are involved in the project. The purpose of this paper is to review the status of the design, as it has been developed so far, emphasizing the design and integration of those components contained within the vacuum vessel of the ITER device. The components included in the in-vessel systems are divertor and first wall; blanket and shield; plasma heating, fueling, and vacuum pumping equipment; and remote handling equipment.