Through a discussion of language use in Kalimantan Barat (Western Borneo) a better understanding of cultural and sociolinguistic phenomena that are relevant to any discussion of Malay identity can be achieved. In this complex setting, the colonial nomenclature of Malay and Dayak, though widely adopted by the people of Kalimantan, does not adequately represent the intricacy and the fluidity of social relationships and identities. Colonial knowledge matches neither the results of linguistic research nor what the Malays and Dayaks know about themselves, their languages and their identities.