Psychosomatic medicine is the term now used to describe the subspecialty of child and adolescent psychiatry that is dedicated to providing mental health services to physically ill children and adolescents. Between 10 and 20 million children and adolescents in the United States are estimated to have an ongoing physical health condition. The risk of a psychiatric disorder in this population is greater than in the general population and such comorbidity poses unique problems and needs effective treatment strategies. Often, psychiatric problems in these children persist over time, e.g., depression, anxiety, posttraumatic stress disorder, or internalizing disorders. This Institute provides evidence-based information to child and adolescent psychiatrists and other mental health providers about the mental health consequences, interventions, and treatments for children with physical illnesses including asthma, irritable bowel syndrome, pediatric organ transplantation, cancer, HIV, and somatoform illness. Understanding the medical and psychological impact of physical illness and available integrated treatments can improve clinical outcomes for these children and adolescents.