Because of a high incidence of weight loss and amyotrophy in patients with hematologic malignant diseases during induction therapy, an analysis of the metabolism of proteins was made in 14 patients, some of whom were receiving parenteral nutrition. Proteins, fibrinogen, amino acids in blood, and nitrogen and amino acids in urine showed hypercatabolism with a very negative nitrogen balance. This disorder is associated with a significant decrease in proteinemia and fibrinemia, which returns to normal during complete remission and in spite of continuation of the same chemotherapy. Total parenteral nutrition does not influence these metabolic disorders during this period. In 2 patients who received total parenteral hypernutrition (TPHN) that provided more calories and more nitrogen (4800 cal and 25 g nitrogen), nitrogen balance tended to zero despite high urinary nitrogen excretion; proteinemia and albuminemia remained normal. Here, TPHN was well tolerated, induced a compensatory hypercatabolism with a high quantity of calories and nitrogen and, thus, decreased morbidity risks during induction treatment by correcting the metabolic disorders; also, tolerance to chemotherapy was considerably improved.