Abnormal levels of serum enzymes have been observed in a number of diseases.1-4Attention has been particularly devoted to the study of the serum glutamic oxalacetic transaminase levels in patients with cardiac and hepatic disease.2,3There has been no systematic study of the serum enzymes in patients with anemia. In a study of lactic dehydrogenase levels of the serum in patients with various diseases4it was found that the levels of this enzyme were elevated in patients with megaloblastic anemia and in those with sickle-cell disease but not in patients with a number of other types of anemia. The present study constitutes an extension of these observations. The levels of lactic dehydrogenase and glutamic oxalacetic transaminase have been studied in patients with megaloblastic anemia, hemoglobinopathies. other hemolytic anemias, and anemias of other causes. Materials and Methods The serum levels of lactic dehydrogenase (LD) were determined by a