This article examines the way in which mobile telephony is used in public places. Early research on the "nomadization" of the telephone rapidly identified clashes between use of this technical object and the normative expectations of individuals sharing a public context. Based on a large number of "naturalist" ethnographic observations, the author examines the way in which individuals (users or non-users, alone, in company, etc.) adjust their use in relation to different public contexts (in the street, in a railway station, on a train, in a caf? or restaurant).