This chapter reviews research on the phonetic and phonological production patterns of children exposed to two or more languages in early childhood. Much of the research has examined whether bilingual children differ from monolingual children in their production patterns and, when differences have been found, whether such patterns can be explained by language-internal (e.g., the influence of the phonological properties of one language on the other), language-external (e.g., language input or dominance), or other factors (e.g., the developing lexicon). We focus on language-internal influences, also referred to as cross-linguistic interaction, and review models that have been used to account for interaction. Our findings reveal that, while systematic differences between monolingual and bilingual speech exist, the differences are not large and may be explained by multiple factors. The chapter concludes with a discussion of research limitations which include small participant numbers and a predominance of certain language pairs, factors that have hindered attempts to model cross-linguistic interaction.