We report a case of acute respiratory failure due to refeeding syndrome caused by hypocaloric enteral tube feeds. A 60-y-old obese man, with a diagnosis of esophageal carcinoma with local metastases, underwent feeding jejunostomy tube insertion. Enteral tube feeding was initiated at small volumes providing 4.4 kcal x kg(-1) x d(-1) and gradually increased over 48 h to 29 kcal x kg(-1) x d(-1) (based on adjusted body weight). The patient then developed acute respiratory distress requiring intubation and ventilatory support. Serum phosphorus (P) level was extremely low at <0.7 mg/dL. Serum potassium (K) and magnesium (Mg) levels were also low. It took >4 d to adequately correct the electrolyte derangements. Successful liberation from mechanical ventilation was then possible. In chronically malnourished patients undergoing nutritional support, even hypocaloric feeding should be considered a risk factor for developing refeeding syndrome leading to severe and acute electrolyte fluid-balance and metabolic abnormalities.