Clinically significant sleep disorders affect at least 10% of the general population. In adulthood, a great variety of aetiologies may be behind symptoms that arise during sleep. The majority of cases can be diagnosed on the history alone without the need for further investigations. For example, if sleepwalking (somnambulism) has continued since childhood and the clinical picture has not substantially changed over the years, no further investigations are indicated. An eye witness account is essential, particularly in cases where the patient either is not aware or is only partially aware of the events. The assessment of symptoms is important since some of them may be associated with various risks and others warrant further investigations. Should the symptoms recur frequently, or be otherwise distressing, and require medication or other forms of treatment, it is recommended that expertise in the field of sleep medicine is sought.