Research on the cognitive processing of speech indicates that the probability of correct identification of words is an insufficient indicator of how reverberation time (RT) affects speech communication. Speech communication under unfavourable reverberation conditions means that a larger part of the limited working memory resources must be allocated to the phonological coding of the speech. Less resources therefore remain for the further processing of speech: integration of current information with previously presented parts of the speech and with permanently stored information and the more permanent storing of new information. Even if reverberation conditions allow the identification of almost all words they may therefore have the effect that the spoken message is less well understood and remembered. Effects of the RT on the listener’s cognitive load, fatigue and learning are discussed from this perspective. It is argued that we need studies of reverberation effects in realistic long-lasting speech communication situations to better understand the effect of RT on speech communication.