Consultation-psychiatry has grown rapidly and become a subspecialty of psychiatry in the past decade. The author reviews the history of this field at the interface of psychiatry and medicine, offers its definition, and discusses current trends pertaining to the organization of liaison services and to the teaching and research activities of liaison psychiatrists. He concludes that a liaison service has become a recognized division of a general hospital psychiatric unit for the provision of psychiatric consultation and teaching to the nonpsychiatric departments of the hospital. Consultation-liaison psychiatry (or liaison psychiatry for short) has emerged in the past decade as a subspecialty of psychiatry, one concerned with mental health problems among medical and surgical patients. Diagnosis, treatment, study and prevention of psychiatric disorders in those patients constitute the proper domain of liaison psychiatry. I will review in this article the major current trends in this field as they pertain to matters of organization, education, and research. A brief historical note and a definition of liaison psychiatry will introduce my review.