From October 1989 to June 1990 we have evaluated at diagnosis and after six months of treatment the nutritional status of 21 oncologic patients younger than 14 years. At diagnosis, 14% of the children showed slight malnutrition on anthropometric evaluation, although there were biochemical data of protein malnutrition in 47% of the cases. Children with abnormal anthropometric measurements and those with a high risk of becoming malnourished (infants with advanced abdominal diseases) were given dietary supplements. In the follow-up evaluation, 90% of the patients showed normal somatic indexes and 76% showed recuperation in their protein values. The recovery of the nutritional status was most important in the group of patients with Acute Lymphoblastic Leukemia.