This paper addresses the issue of directionality in simultaneous interpreting by exploring professional Chinese/English interpreters’ experience of simultaneous interpreting, focusing specifically on the impact of language direction on their choice of strategies. Ten professional interpreters interpreted two speeches from English into Mandarin Chinese, and two speeches from Mandarin Chinese into English, each followed by a stimulated retrospective interview. The processes which seemed to be at work in their simultaneous interpreting were explored through a qualitative analysis of their retrospections, and a model was constructed on the role of professional practitioners’ use of strategies in each of the two directions. The results suggest that professional interpreters who must regularly work in both directions may develop strategic approaches to cope with the different demands of A-to-B and B-to-A interpreting. The differences seem to be a result not only of the asymmetry between their A- and B-language proficiency, but also of the strategies available to them, their metacognitive awareness of the limits of their language abilities, their audience’s expectations and other norms they believe apply to their performance, as well as the discourse structures of their working languages.