To evaluate the extent of the nutritional stress of pediatric bone marrow transplantation (BMT) and to evaluate the use of total parenteral nutrition (TPN), 35 consecutive pediatric patients who received BMT were studied retrospectively. Voluntary cessation of oral nutrition in almost all patients was observed, and significant decreases of serum albumin levels were seen after BMT. In 85% of these patients, TPN was necessary in response to severe wasting and fasting. No deaths were related to indwelling central venous catheters during the period of 2968 catheter-use days in these severely myelosuppressed patients. The mean of the total daily energy intake was 104% of basal energy expenditure (BEE), and 70% of patients lost their weight. Predicted energy requirement to maintain body weight after BMT would be 128% of BEE from a simple linear regression step in this study. Significant correlations were found between the marrow recovery time and the initial nutritional state, expressed as the percentage of ideal weight height ratio, as well as benign nature of the disease. The use of TPN did not show any beneficial effects on the time course of marrow recovery, although it showed favorable effects on the maintenance of body weight.