This article reviews recent research on bilingual phonological development and describes the nature of bilingual phonology, focusing on characteristics of cross-linguistic influence on bilingual phonological abilities. There is evidence of positive and negative transfer (acceleration and deceleration) on children's phonological abilities. Several methodological issues limit the ability to generalize findings from previous research to larger groups of bilingual children (e.g., small sample size, lack of consideration of age of acquisition of each language, and language abilities of the participants). Sources of heterogeneity in language development are presented and discussed. Phonological abilities are related to language abilities in bilingual first language learners of English and Spanish. Empirical evidence from research in our laboratory supports this claim. We discuss implications of research findings and limitations for future research and clinical practice. We provide specific recommendations for bilingual research and for clinical assessment of young bilingual children.KEYWORDS: Bilingual, phonology, speech, assessment, language Learning Outcomes: As a result of this activity, the reader will be able to (1) discuss sources of heterogeneity in bilingual language and phonology; (2) summarize effects of language proficiency and experience on bilingual phonology; and (3) describe implications of language experience on clinical assessment.Speech-language pathologists (SLPs) face a considerable challenge in accurately differentiating between speech and language disorders and speech and language differences when working with bilingual children. 1 According to annual estimates of population change, the