Dementia is a major public health problem in developed countries and imposes considerable cost and resource commitment on health care systems. Dementia disrupts the functional state of the affected person and their care needs places burden on family members. Early detection of the medical conditions that cause dementia has long been considered important. The first half of this book describes the history and evolution of how the medical profession has conceptualised the syndrome of pre-dementia and the development of our modern understanding of degenerative brain disease. The role of cognitive testing and brain imaging is also described in detail. The second half describes a study that aimed to determine whether or not the presence of subjective memory complaint is a risk factor for future deterioration in brain function.