The next energy-frontier accelerator - A linear e+ e- collider?

Two options for a linear e+e- collider are presently under development, the ILC and CLIC. The energy reach of the two machines is different, which leads to two different technological choices. ILC is based on superconducting acceleration technology, the CLIC design uses a two-beam acceleration system with normal conducting copper cavities. Nevertheless considerable synergy between the two design groups has been developed. The paper will highlight the major differences a well as the status and the plans of both machines.