The results of an investigation of complete intravenous (i.v.) nutrition for 7 months and 13 days in a 43-year-old woman prove that a good nutritional state can be maintained for a long time, in cases where oral feeding is impossible, by i.v. administration of fat emulsions supplemented with a complete L-amino acid mixture, carbohydrates, electrolytes, vitamins, trace elements and water. During the period of treatment her nutritional condition improved and she gained 10 kg in weight without fluid retention. A mild anemia developed, however. Some interesting findings of this study were: (1) in preventing thrombophlebitis the intermittent i.v. administration was found superior to the continuous method; (2) the weight gain was considered to be caused by fat deposition in the existing cells; (3) a positive nitrogen balance was obtained at 4.0 g N and 1,830 kcal/day; (4) the composition of the adipose tissue was reversibly influenced by the fat emulsion, Intralipid; (5) the plasma cholesterol values increased in spite of the administration of about 50 g of linoleic acid/day; (6) the effects on the liver were mild as judged by liver biopsies and liver function tests, and (7) a tendency to megaloblastic anemia was caused by treatment with phenytoin and could be counteracted by an increased i.v. administration of folate.