This study investigated the degree to which Portuguese students (n=100) educated in France switched or mixed languages in a written essay. Subjects were told to express themselves liberally in either or both languages. A linguistic history was also taken for each student. The measures were administered in a French-language school, and instructions were given in French. Both qualitative and quantitative code-switching analyses were performed on the texts. Most students, 71.4%, used exclusively French, and 6.1% used exclusively Portuguese. About 9% used mostly French and about 10% used mostly Portuguese. Just over 3% alternated languages without apparent dominance of either. Alternation of languages was categorized as either lexical or syntactic. Language mixing was much more frequent in Portuguese than in French. Six types of mixing were distinguished, and the relative occurrences of the types in the two languages were assessed. Implications for instruction in a second language are examined. (MSE)