The present paper compares telephone interpreting and on-site interpreting in order to investigate the ways in which social interaction in these different interpreting situations is influenced by the setting. Two real-life encounters recorded at a police station are used to illustrate and explore differences in the participants' - including the interpreter's - conversational behaviour. The encounters involved the same participants and concerned the same case. In one encounter, the interpreter communicated by telephone, in the other she was present on site. The on-site exchange was strikingly more fluent, compared to the telephone-interpreted one. The difference is made manifest discursively, for instance in the average length of the participants' turns at talk and in the patterns of overlapping speech. It would appear that a significant difference between the two types of interpreter-mediated encounters lies in the possibilities they provide for the participants to coordinate and to synchronize their collective activity, or interaction. [Source: abstract in journal]