Before I started writing this chapter, one of my colleagues asked me why I was including a discussion on the mentally ill in a book on interpersonal relations. It was a good question, and one for which I did not immediately have an answer. This is not, after all, a book on abnormal psychology. Yet I intuitively felt that this inclusion not only made sense but that it was critical. Accordingly, I begin this chapter by explaining why understanding people with psychiatric disturbances, in addition to being an important topic in its own right, has significant implications for ordinary human relations.