  This report, Volume IV of the International Linear Collider Reference Design
Report, describes the detectors which will record and measure the charged and
neutral particles produced in the ILC's high energy e+e- collisions. The
physics of the ILC, and the environment of the machine-detector interface, pose
new challenges for detector design. Several conceptual designs for the detector
promise the needed performance, and ongoing detector R&D is addressing the
outstanding technological issues. Two such detectors, operating in push-pull
mode, perfectly instrument the ILC interaction region, and access the full
potential of ILC physics.
