The behaviors associated with illness are different depend upon individuals even if Patients complaints same symptoms and have same disease. Understanding the patterns of those behaviors become one of the important elements in determining the diagnostic and treatment approaches and treatment compliance. The sick role plays a essencial part in abnormal illness behavior. The characteristics of abnormal illness behavior ran be applied to many parts in medicine. In case of the various kinds of functional disorders whose organic foundations are obscure and in applying the cognitive therapy, rehabilitation program and occupational therapy, the assessment and evaluation of the abnormal illness behvior is known to be beneficial. For improving the comprehensive psychiatric treatments which could be applied to the Koreans more effectively in patients with somatoform disorders and other various kinds of neurotic disorders further researches especially on the medico-historical and socio-cultural aspects of the illness behavior should be followed. And understanding the abnormal illness behavior would be helpful in enhancing the medical cost effectiveness.