Detector concepts for a linear collider

The particle physics community has chosen an e**+e**- linear collider as the next facility after the LHC. The physics aims of this machine call for high-precision measurements and need detector properties somewhat different from the recent developments for the hadron collider. This paper reviews the present detector concepts, and the ongoing R&D on vertex detectors, tracking devices, electromagnetic and hadron calorimeters undertaken in order to fulfill these demands.