Thirteen girls aged between 14 and 17 years were included in an open study assessing the effect of Dipiperon in behavioural disorders in an orthopedagogic setting. Initially, patients received Dipiperon under open conditions for 3 weeks (phase 1) and those who showed good improvement then entered a placebo-controlled double-blind trial (phase 2). Dipiperon was administered as 40 mg tablets twice daily. Placebo tablets were identical in appearance to Dipiperon tablets. Behavioural changes were evaluated using a 39 items rating scale. During phase 1 significant improvement was obtained for 17 items of the 39-item rating scale. In the double blind phase significant deterioration occurred for 12 items in the placebo group whereas the Dipiperon patients remained virtually unchanged.