This volume brings together a collection of empirical studies on phonological acquisition and disorder of monolingual children speaking different languages (English, German, Putonghua, Cantonese, Maltese, Telugu, Colloquial Egyptian Arabic and Turkish) and bilingual children speaking different language pairs (Spanish-English, Cantonese-English, Mirpuri/Punjabi/Urdu-English, Welsh-English, Arabic-English and Putonghua-Cantonese). The research findings provide much-needed baseline information for clinical assessment and diagnosis as well as valuable evidence concerning theories of language acquisition and the role of the ambient language.