Designers are increasingly being urged to take account of the situated and contingent organisation of the work that their systems are to support or automate. Within CSCW the concept of work-practice is a much used token for the organisation of work. This paper develops the debate about the position of work-practice in design by recognising that it is an ambiguous concept in sociology that is used to refer to different orders to work organisation. It is argued that as such it is as likely to mask the situated and contingent organisation of work as it is to make it visible. In order to fully realise the radicalisation of design portended by the deployment of the concept of work-practice and in order to make visible the in situ organisation of work it is argued that full and due weight has to be placed upon grounding the concept in analytic explications of the interactional ordering of work. This stands in contrast to grounding work-practice in the formalisms of work emanating from theoretical debates about work in a capitalist economic/social structure; documentations of work; the narratives of workers, managers, and purchasers; dialogues with users, and mere observations of work. Two studies are invoked to substantiate this argument, one involving a sales ordering and invoicing system, the other a crime reporting system. © 1996 Kluwer Academic Publishers.