This study investigates the use of pronouns nous and a subgroup of on in a corpus of advanced oral and written French interlanguage produced by 32 Dutch L1 speakers. The subject nous + first person plural verb is characteristic of formal styles while on + third person singular verb is typical of informal styles. A quantitative analysis of the oral corpus revealed that the amount of authentic interaction, but not the amount of formal instruction, in the target language is significantly related to the choice of on. Its use correlated with morpholexical accuracy rates, fluency, omission of ne in negations and use of colloquial vocabulary. A similar analysis of the written corpus revealed equal proportions of on, which suggests that as a group, the learners had not yet completely acquired the constraints on this variable.