Taurine concentrations in plasma, platelets, lymphocytes, granulocytes, erythrocytes, and urine were measured in 19 children who were undergoing long-term home parenteral nutrition for 27.4 +/- 7.1 (SEM) months. The parenteral solutions contained methionine, but not taurine or cysteine. The patients' plasma, platelet, and urine taurine concentrations were significantly reduced to 54, 48, and 16%, respectively, of the values from normal children of similar ages. The most significant reductions in plasma and platelet taurine concentrations were observed in the children who were estimated to absorb less than 5% of their daily calorie needs from the enteral tract. Lymphocyte and erythrocyte taurine levels tended to be lower but were not significantly different from those in normal children. The patients' plasma methionine and cystine levels were not different from normal. There was a direct correlation between plasma and platelet taurine concentrations and between plasma and urine taurine. Both plasma and platelet taurine tended to be directly correlated with age and, after the 1st yr of total parenteral nutrition, with the duration of total parenteral nutrition therapy.