Vast global resources are ploughed into the delivery of treatment interventions ranging from diet and lifestyle advice to complex surgery. In all cases, whatever the intervention, unless the recipient is engaged with the process and understands why the intervention has been offered and the part they play in its success, compliance is an issue. Even where the individual does engage and understand, he or she may choose not to comply. Non-compliance is estimated to cost the pharma industry US$70 billion per year. No figures exist for the cost to healthcare insurers and public health but non-compliance is undoubtedly one of the top five issues facing both drug developers and healthcare providers. During clinical trials, non-compliance undermines the accuracy of the data generated from the whole trial as well as particular aspects such as the efficacy of different dosages. This book explores the key factors which drive compliance and the part that healthcare professionals can play in improving this, with the key underlying goal of improving public health in its broadest sense.