This TowerGroup Research Note discusses the market drivers behind the rise of the health savings account (HSA) and the health care flexible spending account (HCFSA). The latter provides pretax reimbursement of qualified medical costs not covered by insurance and is referred to more generically by the Internal Revenue Service as a flexible spending arrangement.) The Note compares HSAs and FSAs to earlier types of individual health account products and considers the current market size and growth potential over the next five years.