In this innovative book, the authors set out their theory of Self-in-Relationship Psychotherapy (SIRP), advocating for the integration of relational, self, and physical intimacy needs in the conceptualization and treatment of psychological problems, placing human needs at the center of treatment. This marks a shift in how psychological and relational problems are understood, currently being perceived in terms of affects, cognitive processes and behaviors. Using numerous illustrations from their own clinical practice, Meier and Boivin contend that this understanding overlooks the pivotal role that needs play in all aspects of peoples' personal lives and relationships. Children, adolescents, and adults do not live primarily from feelings and thoughts, but from basic psychological and relational, needs such as wanting to be in a meaningful relationship, having the autonomy and freedom to make decisions about their lives, experiencing being competent, being regarded as a significant and important person, and experiencing emotional, intimate, and sensual and/or sexual connections. By taking such an approach this book stands out among other books on psychotherapy theories. Authored by two seasoned psychologists who have provided therapeutic services to children, adolescents, and adults for 40 years, this book comprises the foundational theory for practicing Self-in-Relationship Psychotherapy, making it of interest to graduate students, clinicians in training, and practicing psychologists, social workers, and psychotherapists alike.