OBJECTIVE: To investigate whether using ecstasy (3,4-methylenedioxymethamphetamine, MDMA) is preceded by symptoms of behavioural and emotional problems in childhood and early adolescence. DESIGN: Prospective, longitudinal, population based study SETTING: The Dutch province of Zuid-Holland. PARTICIPANTS: A sample of 1580 individuals, followed up across a 14 year period, from childhood into adulthood. MAIN OUTCOME MEASURES: The first assessment took place in 1983 before MDMA appeared as a recreational drug in the Netherlands and included the child behaviour checklist to obtain standardised parents' reports of their children's behavioural and emotional problems. Use of the drug was assessed with the composite international diagnostic interview 14 years later. RESULTS: Eight syndrome scales of childhood behaviour were examined. Scores in the deviant range for the scales designated as anxious or depressed in childhood were significantly related to use of MDMA in adolescents and adults, resulting in an increased risk (hazard ratio 2.22, 95% confidence interval 1.20 to 4.11, P = 0.01). CONCLUSIONS: Individuals with childhood symptoms of anxiety and depression may have an increased tendency to use MDMA in adolescence or young adulthood. Its effects are supposed to include enhanced feelings of bonding with other people, euphoria, or relaxation. Especially individuals with symptoms of anxiety or depression may be susceptible to these positive effects.