U ndergraduate courses at N orth A m erican universities, particu­ larly in the sciences, are increasingly being taugh t by in ternational teaching assistants (ITAs). T h e ir com m unication difficulties in the classroom have been the source o f m uch hand-w ringing and com ­ plaint, leading to a burgeon ing n u m b er o f studies. Most previous investigations o f the discourse and in teraction o f these ITAs have a ttem pted to p in po in t th e ir difficulties and failures, specifically, how their perfo rm ance falls sho rt o f that o f native-speaking teach­ ing assistants. In contrast, the outcom e o f the in teraction in the chem istry laboratory sessions in this study is largely successful; that is, the students m anage to com plete the ir experim ents and subsequent reports. T heir com prehension o f the task may be due in large p art to the ir having read the written m aterial provided in the laboratory m anual. However, all questions that arise in the course o f the experim en t m ust be resolved du ring the lab session betw een the NNS (non-native speaker) teaching assistant and the native speaker (NS) underg radua tes in o rd er for the experim ents to be executed successfully.