Chronic leg ulceration is an increasing burden in the UK, both financially to the health service and on a human level. This first article in a four-part series, which looks at leg ulcer management and understanding compression therapy, explores the cardiovascular system, the underlying causes of lower limb problems, and the risk factors for leg ulceration. An overview of how compression therapy works and an introduction to the options available for patients and clinicians in this field of practice is also given. Subsequent articles in the series will look at holistic assessment and clinical decision-making in leg ulcer management, understanding compression hosiery and adjustable wraps, as well as compression bandaging and skin care