The essays in this volume tackle the construction and significance of race and ethnicity as boundary-making processes among diverse immigrant populations in the United States. Race and ethnicity can both unite and divide. The individual scholars contributing to this volume model, deploy, and explain notions of 'borders' and 'boundaries' in various ways, but collectively they emphasize the fluidity of racial and ethnic identities that are shaped, negotiated, and contested in specific contexts and situations. Constructing Borders/Crossing Boundaries also captures the range of spaces in which ethnicity and race become salient—the university, the immigrant enclave, the detention center, the work place, the nightclub, and even the trans-Atlantic passage. This interdisciplinary work features essays on a diverse range of immigrant populations from past to present and will interest scholars from across disciplines.