Hematology is a subspecialty of medicine concerned with the study of blood, the blood-forming organs, and blood diseases. Hematology includes the study of etiology, diagnosis, treatment, prognosis, and prevention of blood diseases.

Hematology combines the disciplines biology physiology, internal medicine, pathology, clinical laboratory work, and pediatrics. Hematologists physicians also very frequently do further study in oncology - the medical treatment of cancer.

Physicians who specialize in hematology are called hematologists. Typical hematologist work includes the care and treatment of patients with hematological diseases, and sometimes work in a hematology laboratory viewing blood films and bone marrow slides, interpreting hematological test results.