Consultation-liaison psychiatry is over 50 years old. Its main goal has been to bring medicine and psychiatry closer together so as to improve patient care in its psychosocial and psychiatric aspects. The history of this field may be divided into four overlapping phases: the beginnings, the organizational phase, the phase of conceptual development, and the phase of rapid growth. The highlights of each phase are outlined. The author concludes that C-L psychiatry has achieved the status of a full-fledged subspecialty of psychiatry, one whose main contribution has been to draw attention of clinicians and researchers to psychosocial aspects of physical illness, and to the psychiatric complications of such illness and of the medical and surgical therapies.