Abstract: In a microprobe system for medical applications particularly for use in neurophysiology and neurosurgery a target determining arrangement is provided which can be mounted on a patients head by means of an adjustable mounting device. An adapter is removably attached to the mounting device and carries a manipulator with a removable probe unit that can be moved by a drive unit which is electrically controllable according to spatial coordinates (x,y,z—respectively, R,&phgr;). The probe unit includes a guide tube for receiving an exchangeable microfiber electrode, which includes sensor areas at its pointed tip for the recording of brain activity signals. The signals can be stored with a PC-interface in a data acquisition unit, which is in communication with an output unit. The manipulator includes a microfiber electrode control unit, for example, an XYZ-slide with locking means as well as a base body for the attachment of the probe unit to the mounting device in a predetermined orientation.