This article investigates children's procedures for constructing oppositional stances in argumentative exchanges. While most previous research on children's arguments entails a monolingual bias, the present analysis focuses on bilingual practices of code-switching in disputes emerging during play activities. Drawing on more than ten hours of video-taped play interaction in a bilingual school setting, it is shown how the language contrast arising through code-switching displays and highlights the affective intensity of oppositional stances. Sequential analyses show how code-switching works to escalate social opposition, often to the peak of an argument, resulting in subsequent backdown or full termination of the dispute. Moreover, in certain participant constellations code-switching may be used to constrain opponents' opportunities to engage in further adversative interaction. Finally, it is argued that an approach to play discourse concerned with children's methods for accomplishing accountable actions allows for a view of bilingualism as socially distributed; that is, as an emergent and interactionally managed feature of discourse.An early version of this article was presented at the 9th European Conference on Second Language Acquisition (EUROSLA 9) in Lund, Sweden, June 1999. Thanks are due to Karin Aronsson and Micke Tholander for comments and discussion on an earlier draft. Financial support from the Bank of Sweden Tercentenary Foundation (Grant No. 96-0639:01-02) and from the Swedish National Agency for Education (Grant No. U2001/1912/S) is gratefully acknowledged.