Hematology is a branch of science that deals with diseases of blood-forming organs such as spleen and bone marrow, as well as blood diseases. Hematology, which is a sub-branch of the department of internal medicine, mainly examines diseases in two groups as benign (non-cancerous) and malignant. Examples of benign diseases are anemia, bone marrow deficiencies, sickle cell anemia, Mediterranean anemia (thalassemia), multiple myeloma, bleeding and coagulation disorders, thrombocytopenia and swelling in lymph nodes. Malignant diseases can be listed as blood cancers or leukemias. Hematology, as in many medical fields, is a branch that requires a multidisciplinary approach. It is also extremely important to provide an appropriate nutritional program and psychological support to patients with blood diseases that require close cooperation with departments such as medical and radiation oncology, accompanied by a dietician. Bone marrow transplantation has an extremely important place in the treatment of hematological diseases. For this reason, it is important to have fully equipped units and an experienced team in the hospital where treatment is applied.