Abstract: An ambulatory electroencephalography (EEG) system includes a self-powered recording apparatus adapted to be worn by a patient. The recording apparatus includes an A/D converter and a digital memory capable of storing digital data representing analog waveform signals derived from a large number of electrodes secured to the patient. Recording of digital waveform data is governed by a controller, which upon the occurrence of a neurologically significant event (such as actuation of a switch by the patient or detection of EEG waveforms indicating a seizure state) causes the storage of waveform data over an interval immediately preceding the event and immediately following the event.