Effect of antileukemia chemotherapy on marrow, blood, and oral granulocyte counts. This study was designed to elicit the effects of antileukemia chemotherapy on marrow production, blood carriage, and oral extravasation of granulocytes, and on the phagocytic activity of those harvested from the mouth. Fifteen adult patients with various morphologic forms of acute leukemia were followed through one to four courses of chemotherapy. Oral saline rinse samples were obtained thrice weekly and prepared for enumeration in a hemocytometer. The oral granulocyte counts were compared with concurrent counts in the bone marrow and peripheral blood. Phagocytic activity of the oral granulocytes was measured by the method of Smith and Rommel. The 15 patients were followed through 30 courses of chemotherapy and recovery. During each, there was a drug-induced decrease in marrow, blood, and oral granulocytes that was reversed when therapy was discontinued and bone marrow activity was restored. Phagocytic activity of the oral granulocytes was not perceptibly affected by the antileukemic drugs. Oral granulocyte counts provide a noninvasive method for monitoring the onset and recovery of chemotherapy-induced myelosuppression and granulocytopenia in patients with leukemia. 