In this article I aim at developing a phenomenology of illness through a critical interpretation of the works of Sigmund Freud and Martin Heidegger. The phenomenon of "Unheimlichkeit"--uncanniness and unhomelikeness--is demonstrated not only to play a key role in the theories of Freud and Heidegger, but also to constitute the essence of the experience of illness. Two different modes of unhomelikeness--"The mind uncanny" and "The world uncanny"--are in this connection explored as constitutive parts of the phenomenon of illness. The consequence I draw from this analysis is that the mission of health care professionals must be not only to cure diseases, but actually, through devoting attention to the being-in-the-world of the patient, also to open up possible paths back to homelikeness. This mission can only be carried out if medicine acknowledges the basic importance of the meaning-realm of the patient's life--his or her life-world characteristics.