Psychoimmunology is a rapidly maturing area of scientific endeavor that provides a compelling integrative link between the immune system and its response to stress and psychiatric illness. Stress initiates pathological changes by activating the immune and endocrine systems. Inflammation is at the core of the complex and interactive systems that both contribute to and result from psychopathology. Consequently, inflammation research advances our knowledge of the pathology of depression, schizophrenia, chronic fatigue syndrome, posttraumatic stress disorder and a host of co-morbid conditions, notably diabetes, cardiovascular disease and cerebrovascular disease. The possible mechanisms underlying the bidirectionality of co-morbid medical and psychiatric disorders can be viewed as a consequence of inflammatory changes. These emerging novel concepts illustrate how the knowledge of inflammation can enable meaningful integration of psychopathology with physical co-morbidity. The innovative articles in this volume highlight the intricate link between psychiatry and psychoimmunology and underscore the central role of inflammation in furthering our understanding of the pathophysiology underlying mental health and illness.