Intravenous glucose tolerance, insulin response to glucose, the sensitivity of the periphery to insulin as well as growth hormone and somatomedin levels were determined in osteosarcoma patients and control subjects matched by age, sex, weight an length. The insulin response to glucose and the peripheral sensitivity to insulin were evaluated by using the individual blood glucose and plasma insulin curves for parameter identification in a mathematical model. The mean glucose tolerance was significantly decreased in the patients, most likely due to decreased peripheral insulin sensitivity. Plasma growth hormone levels were normal in all patients which was also the case with somatomedin levels determined by both radioreceptor- and radioimmunoassay.