Children with cancer represent a high-risk group for protein-energy malnutrition due to side effects associated with treatment. Assessment of nutritional status at the time of diagnosis and during treatment is, therefore, essential for planning nutritional intervention. We studied the nutritional status of 25 children with leukemia [9 newly diagnosed/relapsed (D/R) leukemic patients and 16 children with leukemia in remission (REM)]. Plasma proteins (prealbumin, PA; albumin, Alb; transferrin, Tr; retinol-binding protein, RBP) and acute phase-reactant proteins (alpha 1-acid glycoprotein, AGP; C-reactive protein, CRP; ceruloplasmin, CER) were measured by radial immunodiffusion. Results show that there were no significant deficits in anthropometric measurements among leukemic children. In contrast, the mean levels of all plasma proteins, especially PA (P < 0.005), were significantly lower in the D/R group than in the REM group. All D/R children, compared to 59% of those in remission, had PA levels < 20 mg/dl. Only the D/R group had abnormal levels of RBP, Tr, and Alb. Children who were treated with prednisone had significantly higher mean levels of PA, RBP, and AGP than those who were not receiving prednisone. The mean levels of acute phase-reactant proteins in these leukemic children were comparable to those of healthy children. We conclude that mild/moderate malnutrition is common in leukemic patients at D/R and that PA seems to be the most sensitive indicator of visceral protein status.