A study of four children, two with acute lymphocytic leukemia and two with non-Hodgkin lymphoma, treated for three days with L-asparaginase, suggests that insulin receptors may be involved in the hyperglycemia associated with the use of L-asparaginase. Comparison of insulin receptors of circulating monocytes revealed a marked decrease in their number after treatment. This might also explain the lack of response to insulin treatment in one of the patients with symptomatic hyperglycemia.