The urinary excretion of sulfur-containing compounds was studied in 11 burned patients during the first 10 days after injury. They were all given carbohydrate and fat by parenteral nutrition. Two patients also received large amounts of amino acids including methionine, whereas five patients were given amino acids including moderate amounts of methionine and cysteine. A sustained high excretion of mercaptolactate occurred in most patients. The excretion was not influenced by the type of parenteral nutrition, but related to the area of burned skin. A normal excretion of methionine, cyst(e)ine, inorganic sulfate, taurine, mercaptoacetate, thiosulfate, and thiocyanate was found at the end of the observation period in patients without amino acid therapy. Increased amounts of inorganic sulfate and methionine were excreted in patients receiving high doses of methionine, whereas an increased cyst(e)ine and taurine excretion was the most prominent finding in patients receiving moderate amounts of methionine and cysteine. These results indicate that burned patients have an unimpaired ability to metabolize sulfur amino acids. Patients not receiving amino acids or receiving moderate amounts of cysteine and methionine showed a negative sulfur balance, whereas patients given high doses of methionine maintained sulfur balance at near-zero levels. However, since signs of hepatic dysfunction appeared in the latter group, parenteral nutrition with amino acid mixtures containing high amounts of methionine is not recommended during the catabolic phase for burned patients.