Communication between German physicians and immigrant patients is very often difficult because many immigrants have only limited proficiency in German. Therefore, the bilingual constellation is partially “transparent” (Müller 1989). This means that contributions in German are – to some extent – accessible for patients. In this paper the author investigates how the patient’s limited proficiency influences the course of interaction in consultations where an ad-hoc-interpreter is present. The author’s claim is that it changes the interaction format of interpreter-mediated communication. Thus, the patient’s limited proficiency in German is taken as a resource that helps enhancing communication and establishing a smooth flow of discourse. The paper is based on discourse data from projects on ad-hocinterpreting for Turkish and Portuguese patients in German hospitals.