The detection of epileptiform discharges in electroencephalography recordings is a crucial part in diagnosing epilepsy. Thorough electrophysiologic evaluation yields information that allows for tailored surgical therapy in many cases, and thus improves treatment outcome. In recent years, fast activity (>60-80Hz) has been investigated for its diagnostic value in addition to well-known patterns such as epileptic transients. It was shown that these high frequency oscillations are highly specific for epileptic network function and might provide valuable information for localization of epileptic networks and understanding of their mechanisms. In this review, an overview of the electrophysiologic characteristics, putative cellular and network mechanisms in epilepsy is given. Recent studies are reviewed and interpreted in the context of a common hypothetical model.