We investigated boundaries and overlap between somatization and hypochondriasis on different levels of psychopathology: (1) comorbidity between hypochondriasis and somatization on the level of diagnoses in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV; American Psychiatric Association, 1994); (2) comorbidity with other mental disorders; (3) differences in clinical characteristics; and (4) overlap on the level of psychometric measures. The sample consisted of 120 psychosomatic inpatients. Somatoform, hypochondriacal, and depressive symptomatology, cognitions about body and health, and further aspects of general symptomatology were investigated. Diagnoses of Axis I and II were based on DSM-IV. Our results suggest a large overlap on the level of DSM-IV -diagnoses: only 3 of 31 hypochondriacal patients had no multiple somatoform symptoms, while 58 of 86 patients with multiple somatoform symptoms had no hypochondriasis. However, the overlap between hypochondriacal and somatization symptomatology on the level of psychometric measurement is only moderate, indicating that hypochondriasis is a markedly distinct aspect of somatoform disorders.