This work provides a phenomenological account of the experience of illness and the manner in which meaning is constituted in the physician-patient relationship. Rather than representing a shared reality between physician and patient, illness represents two quite distinct realities--the meaning of one being significantly and qualitatively different from the meaning of the other. This difference in meaning has important implications for medical practice in terms of achieving successful communication between doctor and patient, alleviating the patient's suffering and devising maximally effective therapeutic interventions. In disclosing the manner in which the individual constitutes the meaning of his experience, the phenomenological analysis reveals that physician and patient constitute the meaning of illness from within the context of different "worlds'--each "world" providing its own horizon of meaning. The difference in perspectives between physician and patient reflects a distinction between meaning which is grounded in lived experience and meaning which is not so grounded (between the "natural attitude" and the "naturalistic attitude"). This distinction is evident in the manner in which both illness and body are experienced differently by physician and patient. In particular, the illness constituted by the patient is distinct from, and cannot be identified with, the disease state constituted by the physician. A phenomenological analysis of body reveals that illness is fundamentally experienced by the patient as a disruption of the "lived body" rather than as a dysfunction of the biological body. This disruption of "lived body" incorporates the disorder of body, self and world and may include the disturbance of lived spatiality and lived temporality. Illness may cause the patient to objectify his body as a malfunctioning physiological organism but this conception of the body-as-object by the patient is significantly different from the physician's constitution of the body-as-scientific-object. There are certain essential characteristics which pertain to the lived experience of illness regardless of its idiosyncratic manifestation as a particular disease state. In recognizing these essential characteristics and in explicitly attending to the patient's meanings, the physician can effectively minimize the difference in understanding between himself and his patient.