Sleep-walking, which is a fairly frequent symptom in children, is less common in adults, and, though fascinating, this subject has not yet received as much attention as its importance deserves. In the Text-Book of Medicine edited by Price there is no mention of this symptom. In the medical and legal literature one often comes across the same case-histories quoted by successive writers, some of whom consider somnambulism a hysterical dissociated state, while others maintain that it is an epileptic phenomenon. A correct diagnosis is essential not only for the purpose of treatment, but also for assessing criminal responsibility. Unfortunately, the features stated to be characteristic of somnambulism would seem really to be due to more than one condition.