As the average age of the population rises, mental health professionals have become increasingly aware of the critical importance of personality in mediating successful adaptation in later life. Personality disorders were once thought to “age out,” and accordingly to have an inconsequential impact on the lives of the elderly. But recent clinical experience and studies underscore not only the prevalence of personality disorders in older people, but the pivotal roles they play in the onset, course, and treatment outcomes of other emotional and cognitive problems and physical problems as well. Clearly, mental health professionals must further develop research methods, assessment techniques, and intervention strategies targeting these disorders; and they must more effectively integrate what is being learned from advances in research and theory into clinical practice. Inspired by these needs, the editors have brought together a distinguished group of behavioral scientists and clinicians dedicated to understanding the interaction of personality and aging. Offering a rich array of theoretical perspectives (intrapsychic, interpersonal, neuropsychological, and systems), they summarize the empirical literature, present phenomenological case reports, and review psychodynamic, cognitive-behavioral, and pharmacological treatment approaches. This comprehensive state-of-the-art guide will be welcomed by all those who must confront the complexity and the challenge of working with this population.