A study investigated the characteristics and behaviors of college students learning a third language. Four groups of students with backgrounds in Slavic second languages and enrolled in a variety of Slavic and non-Slavic third languages courses were studied using ethnographic techniques, including open-ended questionnaires, focus groups, classroom observation, and interviews. Subjects were from three programs: a 1993-94 program in languages of the former Soviet Union at the University of Maryland at College Park; a language cross-training program at the Defense Language Institute Foreign Language Center (California) (DLI); and a DLI study of the effectiveness of foreign language immersion training. The proficiency outcomes of third-language learners were compared with those of learners in similar second-language courses. Two results emerged: (1) third-language learners are highly successful; they learn more language faster than second language learners of the same target language; and (2) their behaviors are those of the self-directed learner. Implications of self-directed second-language learning for the learner of less commonly taught languages and for learning outside formal language programs are discussed. Contains 88 references. (MSE)