This thesis explores the subject of identity development during late adolescence by analyzing research from three studies: "Self-concept and questions of life: Identity development during late adolescence" (Adamson and Lyxell, 1996); "Adolescent identity--a qualitative approach: Self-concept, existential questions and adult contacts" (Adamson and Hartman, 1999); and "Identity: A developmental study of adolescents' self-concept" (Adamson, 1999). Each study asks questions pertaining to three domains: adolescents' self-concept, their existential questions, and their contacts with adult people. Identity development during late adolescence is examined through three empirical questions. First, how do adolescents perceive and describe themselves? Second, what do they consider important in their lives? Third, how do they describe their contacts with adults? Results from interviews, a personality inventory, and sentence completion tasks and question show that a majority of respondents had a positive self-image; an inconsistent self-concept was related to negative factors; existential questions concerned personal future; and adults were needed because of their experience and knowledge. Reprints of the three studies on which this thesis is based are appended. (Contains 168 references, 3 tables, and 3 figures.) (JDM)