During the past 21 years from 1959 to 1979, 238 cases of childhood leukemia were diagnosed at the Pediatric clinic of Chung-Ho Memorial Hospital of Kaoshiung Medical College. The epidemiology and clinical manifestation as well as the result of study on serum lactate dehydrogenase and its isozymes were analized. There was no evidence of increasing prevalence in the recent years in our series. The incidence of male is higher than the female with a M/F ratio of 1.38:1. The age incidence is predominant in early childhood ranging from 3 years to 8 years (51.49%) with a peak incidence at 5-6 years group which was somewhat higher than other studies. Almost all of our patients were acute in type with only 3 cases (1.26%) of chronic myelocytic leukemia. The incidence of acute lymphoblastic leukemia (including AUL: 63.02%) was higher than acute granulocytic type (35.29%), that was similar to the data of Lin in NTUH but different from others. Fever (64.68%), general malaise (41.28%), anorexia (23.4%), bone pain (14.4%) or arthralgia (11.06%) were the major symptoms of acute leukemia. Hepatomegaly (77.02%), pallor (71.66%), splenomegaly (58.30%), lymphnode swelling (57.45%) were noted more than two third of our cases. Bleeding tendency (33.62%), anemia (22.13%), purpura (48.94%), also frequently noted. The clinical manifestation of chronic myelocytic leukemia were extremely different from acute type in such conditions: marked elevation of WBC, huge spleen, thrombocytosis, higher reticulocyte count, mild anemia and slower rate of progression. The treatment of acute Lymphoblastic leukemia (ALL), is more favorable than granulocytic type (AGL). Induction with vincristine and prednisolone, 78.79% of ALL patient achieved complete remission in our series, but only 25% in AGL did. Among the patients of ALL, there were 2 cases of nearly 6-year survival we obtained. Prognosis of AGL still remain poor inspite of intensive therapy with Ara-c, adriamycin or other chemotherapeutics. Hemorrhage and serious infection were the major causes of death in our cases. One should pay more and more attention to the patients during the course of treatment if the absolute granulocyte count dropped rapidly. The critical value is 500/mm^3 for infection and 200/mm^3 for sepsis. There was no need to transfuse platelets for prevention of bleeding if the patients stay away from active bleeding. Moderate to marked elevation of serum lactate dehydrogenase (LDH), with a non-specific isoenzyme pattern change was found in our study. Increment of WBC count correlated with the elevation of total LDH value. But there were no any other evidence and explanation for the isozyme change. The higher the LDH total value the poor the prognosis in acute leukemia and the lower the remission rate in AGL were found. Returning to normal of the LDH total value and izoenzyme pattern after remission were also noted in some cases. But obviously, it needs further confirmation by accumulating much more cases.