We experienced a case of anorexia nervosa (AN) associated with refeeding syndrome (RS). The patient was a 24-year-old woman who was taken to the hospital emergency room in a hypoglycemic coma as a result of aggravated emaciation due to AN. On the admission day, she had severe emaciation (BW, 27kg; BMI, 11.4), malnutritional hepatitis, bradycardia, hypotension, hypothermia and hypophosphatemia. After she was intravenously administered glucose, her level of consciousness rapidly improved. On the 7th day, we started intravenous hyperalimentation (IVH). On the 13th day, she developed delirium. Because the delirium appeared after administration of IVH, we diagnosed her with RS. An EEG study disclosed frequent high-amplitude generalized slow waves. SPECT (99mTc ethyl cysteinate dimer) showed a bilateral decrease in the average blood flow. Regional blood flow was decreased bilaterally in the frontal and temporal lobes, and in the thalamus. After she recovered from the delirium and her state of nutrition improved, follow-up EEG and SPECT studies showed a decreased frequency of generalized slow waves and improved blood flow, respectively. Her serum values of P, K, and Mg had been within the normal ranges in the course of the delirium. Thus, before giving more calories to a severely malnourished patient, a physician should consider the possibility that RS will occur, even when serum electrolytes are within the normal ranges.