The majority of people, in cultures worldwide, seek fulfilment and happiness in marriage and couples relationships. Many mental health professionals now find they are increasingly consulted when such relationships encounter difficulties that threaten the wellbeing of the couples involved. The costs of such difficulties can be high, to society, to children and to other family members, in both emotional and economic terms. Psychologists, psychiatrists, therapists, counsellors and social workers will find in this uniquely comprehensive handbook a critical review of knowledge in this wide field, as well as a guide to best practice in its many areas of intervention. The scope of the handbook includes an overview of healthy, normal marriage processes, the major influences on marital quality and stability, the interaction between individual adjustment, environmental events, and relationship satisfaction, and interventions designed to assist couples to enhance their relationship. The emphasis in the chapters which review research is on explicating the implications of current state-of-the-art knowledge for assessment and intervention with couples. Over half the book comprises detailed guidelines on how to conduct interventions for relationship problems. This includes work on different approaches to couples therapy, adapting couples therapy to the needs of couples in which one partner has significant individual psychopathology, working with just one partner, responding to crises initiated by extramarital affairs, mediating divorce, and working with families in which there are combined marital and parenting difficulties.