In this article I invite a reconceptualization and expansion of the field of second language acquisition (SLA) by examining possible intersections between SLA and the area of language instruction currently referred to as the teaching of heritage languages. I discuss the ways in which the opportunity of broadening SLA-and-instruction research can be seized by current researchers so that it can address the most intractable educational problems involving language. Drawing from current research on bilingualism, I first describe the challenges of providing language instruction for heritage speakers and examine the bilingualism of these unique language learners. I then offer an overview of the questions raised by the study of heritage language learners. Finally, I describe communities of professional practice and existing disciplinary boundaries and conclude with a discussion of the ways in which the field of SLA can draw from other areas in order to affect the educational futures of language minority children around the world and, at the same time, contribute to our greater understanding of the human language faculty. THE PURPOSE OF THIS ARTICLE IS TO invite a reconceptualization and expansion of the field of second language acquisition (SLA) by examining possible intersections between SLA and the area of language instruction currently referred to as the teaching of heritage languages. In proposing a reconceptualization of SLA, I am well aware of the existing disagreement within this field about the relationship between SLA and language pedagogy. Some researchers (e.g., Crookes, 1997;Spolsky, 1990) consider that a relationship between these two areas is fundamental, while others (e.g., Sharwood Smith, 1994) view SLA as engaged in basic rather than applied research and in contributing, not to the teaching of language, but to the understanding of the workings of the human mind while following the methodological standards of quantitative-experimental scientificThe Modern Language Journal, 89, iii, (2005) 0026-7902/05/410-426 $1.50/0 02005 The Modern Language Journal inquiry. My own position concurs with the former. I agree with Ortega's injunctions (this issue) about the role and purpose of research: (a) that research should be inspired by considerations of societal needs, and (b) that in carrying out research we should embrace with genuine concern questions of "for whom" and "for what."In proposing a reconceptualization of SLA, I argue that an intersection between the area of heritage language teaching and SLA responds to Cook's (2002) proposal to researchers to alter the perspective of SLA by including second language (L2) users. I also suggest that a meaningful connection between these two areas would begin to address recent criticisms about the narrowness of SLA (Block, 2003;Firth & Wagner, 1997;Johnson, 2004) by focusing on the complexities of heritage language speakers within whose lives commonplace concepts such as mother tongue, first language, second language, dominant language, and home language become probl...