The nutritional status of children with cancer is clinically important. In an effort to separate the influences of disease and treatment, we studied children at the time of diagnosis. A total of 99 children underwent assessment by 24 hours dietary recall, measurement of body mass index (BMI), and analysis of body composition by dual energy x-ray absorptiometry (DXA scan). The group averages for calorie intake and BMI were close to the median population norms but ranged widely among individuals. As a group the study participants exceeded the Dietary Reference Intake for protein. Nine children (9%) had a BMI <fifth percentile. There were statistically significant but at best moderate correlations between dietary intake and body composition by DXA scan. Twenty-four hours dietary recall may not provide accurate assessment of nutritional status in individual children with cancer at diagnosis. However, DXA scans cannot be undertaken in a timely fashion on all children at this point. Alternative methods of assessment are being explored.