Since LD is widely distributed in several organs and tissues, the serum total LD determination is not helpful in diagnosing a specific organ or tissue damage. But the separation of LD into five isoenzymes improves its specificity. Therefore it is used in the diagnosis of wide variety of conditions such as myocardial infarction, hepatobiliary diseases, pernicious anemia, renal diseases, progressive muscular dystrophy, and pulmonary embolism, etc. This study deals with serum total LD level and LD isoenzymes in various liver diseases such as viral hepatitis, toxic hepatitis, typhoid hepatitis, liver cirrhosis, cholecystitis and/or stone. The results as follows: 1) In normal controls, the mean total LD activity was 213±74 units and the LD isoenzyme distributions were LD2, LD1, LD3, LD4, and LD5 in decreasing order of activities. 2) In patient with viral hepatitis, the total LD activity was increased and also LD4 and LD5 were significantly increased. 3) In patient with liver cirrhosis, the serum totol LD activity was slightly increased but the LD isoenzyme distribution was within normal range. 4) In cholecystitis and/or stone, the total LD activity, LD4 and LD5 were all significantly increased but the degree of elevation was much less than viral hepatitis.