Oxamic acid depressed aerobic lactic acid formation by normal, human leukocytes by only 20-25 per cent. Glyceraldehyde increased lactic acid production. Sorbose-1-phosphate was without effect. Iodacetate inhibited markedly, but fluoride depressed only in high concentrations. The significance of these findings regarding the mechanism of aerobic lactic acid formation by mature leukocytes is discussed.