Enzymes related to bactericidal activities of leukocytes were studied in ascorbic acid deficient guinea pig leukocytes. The activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were not affected either under resting or phagocytizing conditions in ascorbic acid deficiency. Granule bound NADPH-oxidase activity of resting leukocytes also was not altered in ascorbic acid deficiency. However, the extent of stimulation in NADPH-oxidase activity under phagocytizing condition was found to be significantly lower in ascorbic acid deficient leukocytes than that in control leukocytes. Similary, the extent of release of acid phosphatase from lysosomes during phagocytosis was also low in ascorbic acid deficient leukocytes. Ascorbic acid deficiency did not influence the activities of glutathione reductase and myeloperoxidase of leukocytes. The significance of these enzyme changes is discussed in relation to the decreased phagocytic and bactericidal activities of leukocytes in ascorbic acid deficiency.