We studied the incidence of hypophosphatemia in patients during the nutritional recovery syndrome. The charts of 150 patients receiving a complete nutritional assessment for 18 months were reviewed; 45 met established nutritional risk criteria. Only 9 of these 45 had serial phosphorus values measured during nutritional repletion, and 5 of these 9 patients had hypophosphatemia (phosphorus levels less than 0.97 mmol/L). Anthropometric measurements of arm circumference and arm muscle circumference were less than the fifth percentile in all patients developing hypophosphatemia. We concluded that hypophosphatemia is an underrecognized complication of nutritional repletion and that anthropometric measurements may be predictive of patients at risk. All patients with significant malnutrition should be evaluated for this complication of refeeding.