To evaluate whether local oral humoral immunity changes during remission-induction therapy of newly diagnosed acute myeloid leukaemia, 10 consecutive adult patients were investigated during 4 weeks. The concentrations of the oral secretory immunoglobulins A and M were increased during the first 7 days but, when corrected for changes in the salivary flow rate, the secretion rates of S-IgA and S-IgM remained unchanged, relative to the values before chemotherapy. In comparison, the concentrations of the serum immunoglobulins A, G and M were decreased, like the leukocyte and thrombocyte counts, during the first 14 d. It is concluded that the chemotherapeutic agents appear to act differently upon the local plasma cells associated with oral secretory glands and plasma cells in the bone marrow, and that the secretion rate of oral immunoglobulins remains constant during remission-induction therapy.