 Patients treated with methadone or levomethadone of 5 general practitioners practices and 2 specialized clinics who might be able to terminate OST during the next 12 months from the doctors perspective can take part in the study. In addition to baseline examination further assessments take place every 3 months i.e. after 3, 6, 9 and 12 months. The questionnaires include state of health, well-being, social situation as well as drug and alcohol use. Furthermore, the treating doctors are asked every 3 months to fill out questionnaires on infections and other disorders, clinical characteristics, dosage process and drug use measured by urine samples. 