Studies involving patients on total parenteral nutrition (TPN) led to conclusive documentation of the essential role of Cr in human nutrition. These patients developed severe diabetic symptoms including glucose intolerance, weight loss, impaired energy utilization, and nerve and brain disorders that were refractory to insulin. After addition of Cr to TPN fluids, diabetic symptoms were alleviated, and exogenous insulin was no longer required. Cr intake by healthy subjects consuming average Westernized diets is suboptimal; if these subjects experience severe physical trauma or other forms of stress, Cr status may be overtly compromised. Recommendations for daily Cr supplementation of 10-20 micrograms for patients on short-term TPN (< or = 1-3 mos) appear to be adequate. Stable patients on long-term TPN may receive ample Cr from that present in TPN fluids. Because of the variable nature of contaminating Cr, Cr intake and losses of TPN patients should be monitored.