The purpose of this study is to ascertain the major aspects of the theoretical structure of Sartrian existentialism and to examine the portrayal of these in Sartre's fiction. The theoretical investigation is based largely on Sartre's "L'Être et le néant" and "L'Existentialisme est u humanisme." The fictional works are "La Nausée," the trilogy "Les Chemins de la liberté," and "Le Mur." The study is prefaced by an examination of the term existentialism and a brief historical comparison of essentialist and existentialist philosophy. The aspects of Sartrian existentialism discussed are: the question of the existence of God and its importance to Sartre's philosophy; the premise of existence preceding essence; the fact of contingency on absurdity and its attendant nausea; the doctrines of freedom and responsibility; the dilemma of choice, anguish, and commitment; and the themes of authenticity, transcendence, and death.