People who have epilepsy seem particularly liable to certain major psychiatric disorders: a chronic interictal psychosis that closely resembles schizophrenia; and episodic psychotic states, some of which may arise in close temporal relation with seizure activity. These disorders are conventionally referred to as the psychoses of epilepsy although some of the episodic forms would be more accurately described as acute confusional states. These conditions have for long puzzled and intrigued psychiatrists and neurologists, but in recent years this interest has quickened especially among biologically minded psychiatrists in search of a neurological model for schizophrenia. In the psychoses of epilepsy and in schizophrenia converging lines of enquiry, in neuroimaging and in neuropathology in particular, have implicated the mesial temporal structures, the more so in the dominant hemisphere, and comparable abnormalities have been reported.1 This review will seek to identify areas of progress, areas of difficulty, and persisting dilemmas. The precise nature of this relation has taxed clinical observers since before the turn of the century. Over the past four decades a consensus has begun to take shape—namely, that certain forms of epilepsy may act as risk factors for the subsequent development of a chronic interictal psychosis, a syndrome sometimes referred to as the schizophrenia-like psychoses of epilepsy (SLPE). This psychosis does resemble schizophrenia in its phenomenological manifestations,2 3 pursues a similar course, is as responsive to antipsychotic medication, and is largely uninfluenced by concurrent seizure activity. Given these similarities it is reasonable to question whether this comorbidity could not have arisen as a result of a chance association between two relatively common disorders. The answer should lie in community based comparisons of unbiased samples of epileptic and non-epileptic subjects with respect to prevalence of psychosis. Attempts have been made to do this, yielding a prevalence of schizophrenia within an …