Hairy cell leukemia (HCL) is a chronic and relatively rare form of adult leukemia. It is estimated that approximately 2 % of all adult patients with leukemia have this form of disease. While the cause of this malignancy is not known, the origin of the malignant cell is thought to develop from the memory B cell compartment. There are approximately 1,000 new cases of HCL every year in the United States. There is an unexplained larger number of men than women afflicted with this leukemia. This disease is treatable, but not curable. The Hairy Cell Leukemia Foundation is a non-profit organization headquartered in the United States that supports patients and research around the world. The HCLF is dedicated to improving outcomes for patients by advancing research in the causes and treatment of hairy cell leukemia and by providing educational resources and comfort to all those affected by the disease.