Cognitive task performance was assessed in three groups of young people: 10 regular users of 3,4- methylenedioxymethamphetamine (MDMA) who had taken 'ecstasy' 10 times or more; 10 novice MDMA users who had taken 'ecstasy' one to nine times; and 10 control subjects who had never taken MDMA. A computerized battery of cognitive tasks (Cognitive Drug Research system) was undertaken on a day when...