A problematic phenomenon in simultaneous interpreting, is that of anomalous stress, i.e. when the interpreter unexpectedly stresses the 'wrong' word. Since one of the functions of stress in spoken language is to show coherence relations in a text, anomalous stress can lead to comprehension problems for the listener. Examples of anomalous stress produced by a professional interpreter at a live conference were acoustically analysed in relation to stress patterns in the speaker's input. It was found that while the anomalous stress produced by the interpreter did not appear to be directly related to semantic or pragmatic features in the incoming message, it was preceded by stressed elements in the input. Two possible mechanisms are tentatively suggested as playing a role in the occurrence of anomalous stress; firstly, an automatic matching mechanism triggered by salient stress from the input, and secondly, the independent storage of salient prosodic patterns from the input.