Lactate dehydrogenase enzyme was found in animal and human and play important role in gluconeogenesis process. It distributed in all organs, but the mainly distributed in liver. To evaluated the level of lactate dehydrogenase (LDH) in acute leukemia and investigated its clinical significance with other hematological and clinical parameters. Serum lactate dehydrogenase (LDH) level was investigated in 50 patients with acute leukemia, 17 patients with acute lymphoblastic leukemia and 33 patients with acute myeloid leukemia, in addition to 20 healthy control cases. The relationship between lactate dehydrogenase level and blood cells were analyzed. LDH level was significant elevated in acute leukemia cases as compared to control group, also LDH level was statistically significant increase in acute lymphoblastic leukemia than in acute myeloid leukemia (p<0.001). There were positively correlation between LDH and white blood cells, bone marrow blasts and uric acid; on the other hand, there were negatively correlation between LDH and red blood cells, and platelets. Lactate dehydrogenases represented as supplementary enzymatic tool can be used as differentiation marker between the different types of leukemia not only but also, follow up the patients during treatment period.