It is widely known that the hematological manifestations associated with exposure to drugs are dramatic and often fatal. In this paper, drug-induced hematological diseases, which are divided into 6 groups including red blood cell disorders, white blood cell disorders, platelet disorders, aplastic anemia, coagulation disorders, and therapy related leukemia, are reviewed. For each group, We presented a typical case and summerized not only the current state of knowledge about the pathogenetic mechanism but also the diagnostic procedures which are capable of identifying the causal drug. Since drugs can induce almost all hematological disorders, it must be emphasized that the hematologists should always doubt that the laboratory datas or the clinical manifestations might be induced from drugs when they encounter the patients with hematological diseases. And, when the signs of drug-induced hematological diseases are clinically apparent, the suspected causal drug should be stopped as soon as possible. Although it is difficult to identify the causal drug using the present technical procedures in vitro, the patient's plasma or serum at onset should be preserved, anticipating further developement of diagnostic procedures.