A system for monitoring an electroencephalogram of a patient during administration of transcranial magnetic stimulation including a transcranial magnetic stimulation (TMS) system, an electroencephalogram (EEG) monitoring system, and a control system, coupled between the EEG system and the TMS system, that responds to signals provided by the EEG system and controls the TMS system wherein timing of operation of the TMS system does not need to be synchronized to timing of operation of the EEG system. A conductive plastic electrode system for use with the EEG monitoring system is also provided.