Denial is a concept often encountered in literature describing patients' psychological responses to physical illness. Definitions and theories of denial have drawn on clinical, cognitive, psychodynamic, organic, and interpersonal frameworks. Denial is related to other concepts such as lack of insight, self-deception, and anosognosia. Empirical studies have yielded mixed results with regard to the adaptive properties of denial. These results require interpretation in the light of: (1) the definitional complexities of denial; (2) the diversity of methods used for its assessment; and (3) the choice of different clinical samples and heterogeneous outcome measures. The clinical management of maladaptive denial poses a challenging problem which requires consideration of factors pertaining to the patient, the illness, the treating clinician, as well as the patient's social environment. To achieve further clarification of the role of denial in physical illness, future research would benefit from clearer definitions and more refined, consistent methods of assessment. A number of recommendations are outlined.