This article shows how the workforce of Lyons’ Grand Bazar, mainly masculine in the 19th century, has almost become exclusively feminine a century later. Confirming what other studies have shown for other sectors of activity, this evolution is due to the evolution in work organisation : women never « replace » men but are in effect hired for new positions which appear when work division is modified and which are then defined as « feminine ». To understand how the sexual definition of position works it is necessary to use the social construction of the skills attributed to each gender outside the context of the firm. This example also serves to trace the history of work organisation in a department store throughout a century whose evolution is closely linked to the economic health of the firm.