The term Obsessive Compulsive Disorder (OCD) is a label for a variety of syndromes with changing symptom configurations and different intraindividual as well as interactional functions. They are among the most difficult to treat psychiatric disorders. Heterogeneous variables affecting personal development in family, school, and peer-group, as well as genetic or brain organic variables contribute to the development of obsessions and compulsions. In more than 50% of patients with OCD we find one or more of the following disturbances before the outbreak of the disorder: low self-esteem; social deficits; increased anxiety level with increased, latent aggressiveness; striving for 100% security. Behaviour therapy today is the "treatment of choice" for OCD--both in respect of direct symptom reduction as well as the treatment of "causes", co-morbidity and risk factors. Additionally to the use of highly standardised "symptom techniques" individualized, multimodal treatment is necessary in the more severely disturbed patients. Long-term follow-up results show 50-80% success--probably depending on variations in the study samples regarding the type of obsessions and compulsions, the degree of developmental deficits before the occurrence of OCD, actual co-morbidity, and professional as well as private life conditions. Whether and to what degree additional psychotropic medication can enhance the efficacy of behaviour therapy, and whether the high relapse rates of 70% after discontinuation of previously successful drug treatment can be reduced by concomitant or subsequent behaviour therapy, cannot be safely concluded from the currently available studies. Are the non-responders in each of these treatments the responders of the non-responders in the alternative treatment mode?