Children first exposed to English as a second language when they start school are at risk for poor academic outcome. They perform less well than their monolingual peers, matched for socio-economic background, at the end of primary school on measures of language and literacy, despite immersion in English at school. Previous research suggests, however, that some bilingual children do better on phonological awareness (PA) tasks than monolinguals in preschool. Two experiments investigated the effect of language pair on PA by comparing monolingual and bilingual children's syllable, onset rime, phoneme and tone awareness using detection, deletion and segmentation tasks. Experiment 1 compared bilingual Putonghua-Cantonese children with two matched monolingual control groups. The bilingual group had enhanced phonological awareness. However, the monolingual Putonghua speakers performed better on the phoneme detection task. Experiment 2 compared Cantonese-English bilingual children and controls monolingual in Cantonese. While there was no overall group difference in PA, the bilingual children had better tone awareness. The profile of findings is considered for possible explanations of later literacy difficulties. (Contains 6 tables.)