This article briefly describes the fundamental principles and some of the clinical applications of interpersonal psychotherapy (IPT), a time-limited, empirically validated treatment for mood disorders. IPT has been tested with general success in a series of clinical trials for mood and, increasingly, non-mood disorders; as both an acute and maintenance treatment; and in differing treatment formats. As a result of this research success, IPT is spreading from research trials to clinical practice in various countries around the world.