Electroencephalography and Magnetoencephalography have provided valuable information about the brain functioning in psychosis. In the last few years, authors have demonstrated that there are neurophysiological alterations already in the prodromal period, before the development of psychosis. This makes them promising tools for predicting a future transition to psychosis. In this paper we review the latest studies using event-related potentials (ERP) in subjects clinically at high-risk of developing psychosis. We particularly focus in the P300, Mismatch-Negativity (MMN) and P50 paradigms, discussing the main findings, but also the limitations and challenges in electrophysiological studies in this population.