A woman, aged 30, experienced attacks of pathological laughter which began during the first months of life; they meet the qualifying criteria of epileptic laughter. Several attacks were recorded by polygraphy and cinefilm. The attack begins with a feeling of unreality associated with a forced, involuntary smile progressing to full laughter. The patient tried to mask the laughter which was not accompanied by euphoria but was followed by loss of consciousness and automatisms. Only during the latter phase of the previously normal EEG did an ictal discharge appear over the right hemisphere. On the basis of the electroclinical pattern and of a review of the literature, the seizure is tentatively explained in terms of a progressive ictal involvement of temporodiencephalic structures.