The research reported in this paper is carried out in an attempt to address, in a systematic fashion, the question of whether there are qualitative differences in processing between novice and experienced interpreters, and thus to provide strong evidence in favour of one or the other position as well as an empirical base for characterizing the nature of interpreting skill. Rather than attempting to study interpreting in all its complexity, however, this research focuses only on the interpreters’ comprehension processes to permit more detailed consideration of them. Translation and production processes are left for further research. To address the issue of possible differences in compression processing, bilinguals with no interpreting experience are contrasted with experienced conference interpreters with respect to the degree to which their interpreting performance reflects different degrees of comprehension of the source text.