This chapter presents a short history of postictal psychosis (PIP) studies and established clinical pictures of nuclear PIP. It discusses the interrelationship between PIP and interictal psychosis (IIP), results of neuro-imaging studies of PIP, premorbid predisposition (including family history) or risk factors, and PIP-related peri-ictal phenomena including discussion of PIP subtypes. Four different combinations of PIP and IIP have been recognized: progression of PIP to chronic psychosis; PIP changing into IIP without a break during an episode of psychosis; PIP and IIP episodes occurring in an alternating manner; and PIP episodes follow after remission of IIP episodes. As with SPECT studies, only a few depth-EEG studies during active PIP episodes are available, though the results suggest interesting subtypes. Psychopathological features of PIP are highly suggestive of association with bipolar disorder, which is supported by data from different perspectives.