Depersonalization (DP) and derealization (DR) remain poorly recognized in clinical routine. Active exploration through structured interviews is strongly recommended, because patients rarely describe spontaneously their experiences with DP/DR. 143 psychosomatic, first-admission inpatients were interviewed about the 1-month prevalence of DP/DR using the Structured Clinical Interview for DSM-IV dissociative disorders. Additionally, the German questionnaires of the Cambridge Depersonalization Scale, the Dissociative Experiences Scale, the SCL-90-R and the Inventory of Interpersonal Problems were used. In the sample we found a prevalence of 23.1% (N=33) for depersonalization-derealization syndrom (ICD-10 F48.1) and 7% (N=10) for secondary pathological DP/DR. A total percentage of 62.9% reported DP/DR to some degree or other. There was a noticeably high co-occurrence of anxiety disorders in patients with pathological DP/DR. Patients with pathological DP/DR were generally more impaired, suffered many more interpersonal problems and were particularly characterized by introversion. Considering the high prevalence of this phenomenon, more attention should be paid to DP/DR in routine diagnostic procedures, treatment and research.