To examine the diagnostic validity of hypochondriasis, we undertook a preliminary family study. Nineteen probands with and 24 without DSM-III-R hypochondriasis were identified among outpatients attending a general medicine clinic. Seventy-two first-degree relatives of hypochondriasis probands and 97 relatives of control probands were personally interviewed with the use of the Structured Clinical Interview for DSM-IV. These relatives also completed self-administered measures of hypochondriasis, psychological and somatic symptoms, and personality traits. No increase in the rate of hypochondriasis was found among the relatives of hypochondriasis probands compared with the relatives of control probands. With respect to other mental disorders, only somatization disorder was more frequent among the hypochondriacal relatives. These relatives also scored higher on measures of hostility, antagonism, and dissatisfaction with medical care. The findings of this study suggest that hypochondriasis may not be an independent disorder but a variable feature of other psychopathology, one that may include somatization disorder.