This paper engages with the marketing of an emerging technology: Radio Frequency IDentification (RFID). It is based on a lengthy ethnographic field study with a marketing team in a hi-tech corporation. We argue that building market relations for this emerging technology involves three closely intertwined activities: the identification of relevant people and things which can form a constituency into which the product can be launched; the narration of a tellable story which articulates and renders accountable relations of people and things; and the development of a compelling version of this story to provide a basis for ongoing engagement of the putative constituency. Identifying potential members for the constituency, convincing them of the compelling nature of the mobility based story, managing access to the constituency and maintaining internal relations between the marketing team and the rest of the corporate organization are all ongoing aspects of this market building activity. The paper forms a contribution to marketing theory by bringing ideas of constituencies, tellable and compelling stories from science and technology studies research together with insights from the literature on marketing.