Text-based interviews involve asking writers of texts how and why their texts were produced and then interpreting textual features by relating them to social, cultural, and ideological meanings. This case study provides an analysis of the use of text-based interviews in a project investigating what professional identity Business English major students at a Chinese university were constructing. The students were asked to explain why they made certain language choices and content selection in their writing for business scenarios, including business letters, emails, and proposals. The textual features and business content choices in their writing and their rationale for these features were coded in terms of business genre knowledge, which was conceptualised as indexical of professional identity. The same student writing was also used with a select group of international business professionals to elicit comment on whether the student writing met professional expectations and why. The text-based interviews generated data for answering the research questions: What professional identity was discursively constructed by Business English students and how was this identity received by the students' target community of practice? Readers will learn what text-based interviews are and strategies for designing and implementing projects requiring text-based interviews. [This content is provided in the format of an e-book.]