Two groups of Mandarin-English bilingual children (3-5-year-olds, 6-8-year-olds) participated in a picture identification task and a picture naming task in both languages. Results revealed age-related growth in English, but not Mandarin vocabulary. Composite vocabulary was larger than either single-language vocabulary in the younger children but was similar to English vocabulary in the older children. Furthermore, children showed a larger receptive-expressive modality difference in their weaker language (Mandarin) than in their stronger language (English). These patterns indicate rapid growth in English vocabulary along with early stabilization of Mandarin vocabulary despite considerable Mandarin input in the home setting.