The occurrence and course of somnambulism and its correlations with behavioral variables have been investigated annually from 6 to 16 years of age in a sample recruited by random means. The prevalence was highest at 11-12 year. No sex difference was found. Apart from sporadic occurrences, the longitudinal data reveal a group of children for whom somnambulism is rather persistent. But even in this group the somnambulism is usually unrelated to other sleep disturbances (apart from "bad" dreams), deviant behavior or known environmental factors. These children have more inhibited aggression and a more developed mental defence against anxiety as determined by Rorschach tests. At school they appear to be more popular than other children.