‘Nederlanders and buitenlanders: A sociolinguistic ethnographic study of ethnic categorization among secondary school pupils’is a study based on nine months of ethnographic fieldwork among pupils of the vocational track of a secondary school in Venlo, the Netherlands. Many of these pupils had a migration background, and though they were born in the Netherlands, they often referred to themselves as buitenlander (‘foreigner’), Marokkaan (‘Moroccan’), or Turk (‘Turk’), and referred to others without migration backgrounds as Nederlanders (‘Dutch people). In this dissertation, van de Weerd combines ethnographic descriptions of the local context with ethnomethodological analyses of interactions to analyze such self- and other-categorizations. Although the use of categories such as Nederlander and buitenlander are commonly interpreted as straightforward indications of (dis)identification with a country or ethnic identity, it is argued that their meanings are constructed and negotiated in local interactions and are therefore much more complex. The pupils in this study, for instance, regularly discussed categories in association with certain clothing styles, language, or behavior, or jokingly teased each other by speaking negatively about these categories. The dissertation furthermore analyzes the relation between categorization practices and the use of different linguistic resources such as Dutch, Limburgish, Turkish, Arabic, and/or Berber. ‘Nederlanders and buitenlanders’ may be of relevance to researchers interested in categorization in interaction, ethnicity, identification, the effects of diversification outside the metropolitan area, and more broadly, linguistic ethnography and sociocultural linguistics.