Any undue concern with bodily function is often labeled as hypochondriacal. Kellner's Illness Attitude Scales, self-rating instruments, distinguish between generic worry about illness, concern about pain, health habits, hypochondriacal beliefs, thanatophobia, disease phobia, and bodily preoccupations. The Illness Attitude Scales have been used in a number of studies concerned with patients suffering from DSM-III-R hypochondriasis, panic disorder, melancholia, in the medically ill, in pregnant women, during medical procedures such as mammography, and in experiments in therapeutics, such as drug trials. The results of these studies and of clinical investigations suggest that the differential diagnosis between hypochondriacal beliefs (characterized by resistance to reassurance), disease phobia, thanatophobia, and the other less specific illness attitudes, is worthy of clinical attention and may entail prognostic and therapeutic implications. Pilowsky's concept of abnormal illness behavior, unlike the DSM-III-R, provides a framework for such differentiation.