The relationship between hypochondriasis and medical illness. Forty-one Diagnostic and Statistical Manual of Mental Disorders-III-Revised hypochondriacs were accrued from a primary care practice. Seventy-five control subjects were selected at random from among the remainder of the patients in the same clinic. All subjects completed a structured diagnostic interview and standardized self-report questionnaires. Medical morbidity was assessed with a medical record audit and with primary physicians' ratings. The hypochondriacal and comparison samples did not differ in aggregate medical morbidity, although the hypochondriacal sample had more undiagnosed complaints and nonspecific findings in their medical records. Within the comparison sample, higher levels of medical morbidity were associated with higher levels of hypochondriacal symptoms. This occurred primarily because the most serious medical disorders were associated with more bodily preoccupation, disease conviction, and somatization. Within the hypochondriacal sample, no correlation was found between the degree of hypochondriasis and the extent of medical morbidity. 