The present study, in an out-patient setting for substance use treatment in adolescents, examines the effect on treatment retention of a mobile telephone follow-up technique (interactive voice response), with or without personal feedback. Subjects in treatment for substance use disorders will be followed by automated mobile telephone contact with questions about psychiatric symptoms and substance use, and the investigators hypothesize that this technique, including a personal feedback reporting back to the client whether his or her status is changing in one way or another, may increase the treatment retention, possibly by means of an intensified treatment contact.