After initial recovery from acute carbon monoxide (CO) intoxication, some patients occasionally undergo severe neuropsychiatric deterioration, which is called postanoxic delayed encephalopathy (sequelae). This is the clinical report about one patient, a 73-year-old man, diagnosed with delayed encephalopathy after acute CO intoxication. The symptoms of the patient were mental dysfunction including memory impairment and disorientation, abnormal behavior, incontinence and mutism. He had completely recovered after an aonxic episode, but the neurological symptoms that developed were preceded by an interval of apparent normality (the 'lucid interval'). We characterized him as suffering deficiency syndrome of the heart and prescribed for him Bokreongbosim-tang and Guipi-tang, and thereafter his symptoms were remarkably improved. For the evaluation of clinical improvement, we use the Modified Barthel Index (MBI), Canadian Neurologic Scale (CNS), and the Korean version of the Mini-Mental State Examination (K-MMSE)