Although suicide among adolescents has been increasing over the past decade, there are surprisingly few clinical studies regarding teen-agers who have attempted suicide. A previous study showed borderline personality disorder as the most common underlying personality problem among a group of predominantly hospitalized adolescents. This paper focuses on the clinical characteristics of 22 teen-agers with a borderline personality disorder who had attempted suicide. The essential pattern of a borderline personality was a persistent instability in a variety of areas, including interpersonal relations, mood, behavior, and self-image. The most prominent characteristics associated with suicide attempts by these adolescents were a tendency to react severely to loss, poorly controlled anger, and self-defeating impulsivity. Many of the characteristic behavioral symptoms of these borderline patients must be determined by a longitudinal history of the teen-ager's life. Specific treatment approaches are needed for these patients.