Knowing to write effectively is key to communication within the different interfaces of any professional role – client-facing, colleague-facing and/or public-facing. Complaints of poor service from professionals often focus on their failure to communicate, not merely in terms of politeness and consideration, but with respect to a lack of clear explanations underlying professional decisions. In other words, the process of interpreting their specialist body of knowledge to the client appears to be a great challenge. Communication that performs a translation function between the world of the professional and that of the client is ‘interdiscursive’: it involves a fusion of genres. Interdiscursivity also arises in communication within the workplace, for example in seeking or giving authorisation or advice. In this article, we examine the challenges that interdiscursive communication pose, from the point of view of engineering and of health professionals, some of whom are also teachers in these fields at university level. Our findings are based on interviews we conducted with these different groups. We hereby aim to extend the theoretical and contextual framework drawn up by a previous survey study. Although the interview participants show a certain awareness of interdiscursive writing skills, the conclusions drawn from this awareness differ between the groups, as well as between the employed versus the self-employed professionals. While the former group writes in a way that rather disregards the target audience and does not see much sense in learning and training writing skills, the latter group was obliged to find ways of managing the demands they faced.