Parasomnias are classified as dysfunctions associated with sleep, sleep stages, or partial arousals from sleep. The main part of this article is devoted to the parasomnias which occur in slow wave sleep and correspond to a partial arousal during this state, that is: night terrors, confusional arousals and somnambulism. The diagnosis of parasomnias is done on a very precise description of the behavior and on its time of occurrence during the night, the notion of a familial history of parasomnias is also important. Management depends on the age, the frequency of the episodes and the presence or not of a family disruption. Most parasomnias are precipitated by stress, and in the younger subjects by an interaction between ontogenetic characteristics of sleep and immaturity. In the older patients psychological or organic factors must be eliminated.