The effect of bilingualism on the development of phonological awareness of Chinese children was investigated in 2 studies comparing bilingual speakers of both Cantonese and Mandarin with monolingual speakers of Mandarin. Cantonese-speaking children had developed more advanced onset and rime awareness by 2nd grade as they learned Mandarin in school and became bilingual. Bilingualism seemed to accelerate the development of phonological awareness. But the advantage had mostly disappeared by 4th grade. On the other hand, in the 1st grade, Cantonese-speaking children had more advanced tone awareness than Mandarin-speaking children. This was likely because Cantonese has a more complicated tone system than Mandarin.