This study describes head banging behavior of normal, not hospitalized young children. Thirty-three head bangers were observed under normal bedtime conditions. Four characteristic positions of head banging were defined: hands and knees, sitting, prone, and standing or kneeling. The age of onset ranged from 3 to 12 months, and all of the subjects had a history of other rhythmic activities, such as head or body rolling, prior to head banging. Most of the head banging took place at bedtime and in the morning when the subjects awakened. The regularity was described by 25 mothers as "every night" or "almost every night." Head banging sessions lasted between one half hour and four hours. The tempo of head banging ranged from 19 to 52 head object contacts per minute for girls and 26 to 121 for boys. Reaction of subjects exposed to metronome stimulus varied from complete indifference to dramatic cessation of activity. In a follow-up study of this sample of subjects it was found that 14 ceased head banging between 27 and 48 months of age. All of the former head bangers were described by mothers as active children, prone to rhythmic activity in response to musical stimuli. Coordination of the great majority of the children was described as "excellent.".