This book is about the difficulties encountered by mothers and toddlers in the preschool years, and the effectiveness of professional help. We report a major research project which consists of three approaches to intervention: intensive health visiting, family therapy and mother and toddler groups. The core of the book is a trial of how these approaches affect child disorder, mothers' mental health, child development and the state of the marriage. In the early chapters, the study is placed into the context of current thinking and research, considering issues in child and family development. Chapter 2 focuses on the main variables of the study and considers how psychopathology may develop over this period and bring together evidence on its outcome. In doing so, it builds the case for intervention both by looking at how problems begin, how this relates to the development of the child and family generally, and in turn what effects these problems have on development. Chapter 3 describes approaches to helping preschoolers and the contexts in which these have been tried, leading to studies of the effectiveness of intervention. In the final three chapters, research findings on the practical and academic implications of the work are discussed.