Meticulously researched and beautifully written, Fit to Be Citizens? demonstrates how both science and public health shaped the meaning of race in the early twentieth century. Through a careful examination of the experiences of Mexican, Japanese, and Chinese immigrants in Los Angeles, Natalia Molina illustrates the many ways local health officials used complexly constructed concerns about public health to demean, diminish, discipline, and ultimately define racial groups. She shows how the racialization of Mexican Americans was not simply a matter of legal exclusion or labor exploitation, but rather that scientific discourses and public health practices played a key role in assigning negative racial characteristics to the group. The book skillfully moves beyond the binary oppositions that usually structure works in ethnic studies by deploying comparative and relational approaches that reveal the racialization of Mexican Americans as intimately associated with the relative historical and social positions of Asian Americans, African Americans, and whites. Its rich archival grounding provides a valuable history of public health in Los Angeles, living conditions among Mexican immigrants, and the ways in which regional racial categories influence national laws and practices. Molina's compelling study advances our understanding of the complexity of racial politics, attesting that racism is not static and that different groups can occupy different places in the racial order at different times.