Repetitions may occur in human-computer interaction for various reasons; in this paper the constraints on the use of repetitions and their prosodic realization in the communication with a (simulated) automatic speech processing system which is not functioning properly will be analysed. It will be shown that repeats may have certain phonetic and prosodic properties which the respective original utterances do not necessarily display; however, besides these local changes depending on the immediate sequential context, the use of linguistic strategies such as repetitions changes globally throughout the dialogue. Thus, both the occurrence of repeated utterances and their prosodic realization depend on the relationship to global properties of the discourse structure which is partially determined by changes in the speakersÂ’ attitude towards the system.