ITER reached 50% completion of the work required to achieve First Plasma in November 2017. Progress has been made on ITER infrastructure since the 2016 Fusion Energy Conference, most visibly the construction of many key buildings. The key parts of the tokamak assembly building and the tokamak bioshield have been completed. The tokamak building itself will be ready for equipment in 2020. The cryogenic plant and the magnet power supply buildings are complete, and these systems begin commissioning in 2020. The power conversion and distribution area is complete and in operation, and construction has started on the component cooling water system building. Manufacturing of the basic components of the ITER tokamak is also proceeding well. The base and lower cylinder of the cryostat have been assembled on the ITER site. The first modules of the central solenoid and of the six poloidal field coils have been wound. The first winding packs of the toroidal field magnets are complete, as are the first casings, which have been verified to meet the high tolerances required. The first vacuum vessel sector is near completion and demonstrated to meet strict tolerances. The heating and current drive systems (neutral beams, electron cyclotron heating and ion cyclotron heating) are in the final design phase. The sequence of ITER operation from First Plasma to the achievement of the Q = 10 and Q = 5 project goals has been adapted to the Staged Approach to construction, a stepwise installation of all systems. The ITER Research Plan has been revised in 2017 to be consistent with the systems available in each phase. Physics studies focus on the disruption mitigation system, design of the ITER tungsten divertor, and modelling of ITER plasma scenarios. Modelling concentrates on the initial phases of the Research Plan and on the Q = 10 scenario, especially plasma termination.