Most investigations of bilingual language development focus on children acquiring two European languages. Little research has investigated diverse language pairs or compared the influence of the first language on second language development. The study reported here compared the lexical skills of three groups of 11-year-old students from different language backgrounds. Two bilingual groups (first language Vietnamese or Samoan, second language English) and a monolingual control group matched for social class were compared on a series of tasks. The tasks examined English lexical comprehension and use, as well as single word processing on nonword tasks. The results showed that both bilingual groups performed significantly below their monolingual peers in all lexical tasks but not on nonword tasks. There were no differences between the two bilingual groups, despite the fact that the cultural and linguistic backgrounds of each were very different. The findings indicate that despite six years of formal schooling in English, including focused ESL support, bilingual students from both Vietnamese and Samoan cultural backgrounds perform less well than their peers in their understanding and use of the English lexicon. The implications of these findings for theory of bilingual language acquisition, assessment practice and educational policy are considered.