Prolonged total parenteral nutrition (TPN) with solutions containing hydrolyzed casein has been associated with aluminum accumulation in patients with bone disease. We investigated the effects of free amino acids in TPN solution on plasma, urine, and bone aluminum in six patients, five of whom had symptoms of bone disease or documented demineralization. No evidence of aluminum accumulation was found. TPN with free amino acids, containing 42 micrograms aluminum per liter or less, does not lead to aluminum loading in adolescents or adults.