Shifting from one language of interpretation to another (i.e. from language a and language x to language a and language y) is not an unknown phenomenon in mediated interactions between bi- or multi-lingual clients and multilingual interpreters. Typically, this occurs when clients wish to shift to their dominant language and interpreters also have proficiency (and accreditation) in this language. Twenty Australian-based interpreters (out of a sample of sixty) reported engaging in shifting in the course of interpreting. Language combinations and circumstances motivating clients to shift are presented and systematised to show that the two largest groups of potential shifters are clients who wish to revert to their (chronologically) first acquired language and those who shift from a ‘national’ or ‘majority-group’ language to a ‘minority’ or ‘regional’ one spoken in their country of origin. Responses to hypothetical shifts in the language of interpretation are discussed in which interpreter informants provide acceptability judgements of courses of action and justifications for accepting — or refusing to accept — a shift in the language of interpretation.