Rationale: Recent studies showed that ascorbic acid (AA) stimulates proliferation and maturation of T lymphocytes and NK cells. Chemotherapy results in depletion of those cells and thereby an increased infection rate. A pilot study showed low levels of AA in the plasma of several patients after chemotherapy for hematological malignancies. AA suppletion could be beneficial to the recovery of the immune system in these patients. But before an intervention study can be undertaken, further understanding of changing over time of AA levels and the relationship with the immune status after chemotherapy is necessary.