A brief historical introduction traces the evolution of the concept of hypochondriasis. It is suggested that the term should now be used only as a descriptive adjective when there is a morbid preoccupation with health or body. Social and cultural factors are outlined, as well as problems of measurement. The psychopathology, as formulated by Freud and others, is also described. Clinical aspects are discussed under the headings of general symptoms, pain, smell, bodily appearance, sexual, gastro-intestinal, cardio-respiratory, eyes, and ears, nose and throat. Psychiatric syndromes mentioned are: hypochondria as a possible primary state, personality disorders, phobic-anxiety state, neurashthenia, obsessional neurosis, hysteria, depression, paranoid psychosis and organic. In general, hypochondriacal symptoms seem to make the prognosis rather worse. Treatment is to be aimed at the primary condition, which is most commonly depression, anxiety state or conversion reaction.