Much of the literature on study abroad outcomes focuses on language proficiency gains or on the influence of identity factors on opportunities for language learning. A smaller number of studies have looked at the influence of study abroad on participants' identities and have highlighted outcomes that might be placed under the heading of second language identity. Based on a review of this literature and a qualitative, narrative-based study of nine Hong Kong students participating in thirteen- and six-week study abroad programmes, this paper examines the construct of second language identity and its susceptibility to development in study abroad. Three main dimensions of second language identity are identified, related to (1) identity-related aspects of second language proficiency, or the ability to function as a person and express desired identities in a second language setting, (2) linguistic self-concept, or sense of self as a learner and user of the second language, and (3) second language-mediated aspects of personal competence. The study found that most of the students reported developments along all three of these dimensions, although there were variations among individuals that were related both to the duration of the programmes and individual goals and purposes. Copyright © 2012 Walter de Gruyter GmbH.