This article presents the psychodynamic & developmental theories & processes underlying borderline & narcissistc personalities. Several theories are discussed & differential diagnosis of the many pathologies is stressed. A number of treatment techniques are reviewed, as are the roles of transference & countertransference in work with patients. To illustrate both borderline & narcissistic traits, the life of Sylvia Plath, a poet who committed suicide in 1963, is discussed & several excerpts from her work are presented.