This dissertation explores identity construction, mainly focusing on the ethnonational identity of "Japanese," in contrast to that of "non-Japanese" from ethnomethodological and social constructionist perspectives. Within these approaches, identity is not given "a priori" but emerges through sociohistorical contexts and discursive practices at both micro and macro levels. Based on these approaches, the study also attempts to overcome the epistemological and methodological limitations of previous studies. Many studies on identity issues in Japan do not take social constructionist approaches, but regard the identities of Japanese and non-Japanese as fixed and static. Also, many studies in social sciences are theory- or text-oriented, hence lacking in micro level conversational data where participants produce social order and worldviews. On the other hand, others exclusively focus on conversational data, paying little attention to larger sociohistorical contexts behind micro level interaction. The purpose of this study is to integrate micro and macro level analyses and substantiate understanding of identity construction in people's daily lives in Japan. Utilizing Conversation Analysis and Membership Categorization Analysis, the study explores what kinds of identities are constructed, and how they are assigned, asserted, resisted, and negotiated in social interaction between L1 and L2 users of Japanese. The analysis not only reveals the emergence of ethnonational identities but also of many other identities and the shifts among them. It also demonstrates ideological aspects in the construction of "Japanese" identity revealed in the sense-making process on the side of the Japanese participants and resistance offered by the non-Japanese participants. By presenting these data and analyses, this study suggests reconsidering "Japanese" identity as: (a) a sociohistorical and discursive construct; (b) a topic to be investigated, not as a resource for researchers; and (c) participants' accomplishments in social interaction. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]