The present article poses some fundamental questions related to bilingualism and to the acquisition of two phonological components, by very young children. It discusses different types of bilingualism and their outcomes. After a brief consideration of alleged pros and cons of bilingualism brought up in the past decades, two perspectives of bilingualism are sketched—psycholinguistic and sociolinguistic—and certain aspects of bilingual child phonology are presented from each of these points of view. The essential issue is whether different outcomes of bilingual child phonology are predictable, and to find the crucial criteria to support the predictions. Finally, the discussion addresses some basic questions about bilingual acquisition, and ends with a summary of various types of cross-linguistic interaction.