This paper synthesizes research on the acquisition of linguistic variation by learners of French as a second language, an overview that, to our knowledge, is the first of its kind. It also presents a case study on French immersion students' acquisition of pronouns nous and on ('we'), an alternation existing in many varieties of spoken French. The study shows that the students use the mildly marked variant on slightly more often than the formal variant nous, but much less often than do L1 speakers, who use it almost categorically, and immersion teachers, who strongly favor it. It also shows that female and middle class students favor nous, students with greater extra-curricular French language exposure favor on, and students who speak a Romance language at home favor nous. Various explanations are proposed for these correlations. Finally, the students, like L1 Francophones, favor on in linguistic contexts where the referent is both non-specific and unrestricted.